At first, it complains about some missing Physix headers e.g.:
Severity	Code	Description	Project	File	Line	Suppression State
Error (active)	E1696	cannot open source file “Px.h”	UE4	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Public\PhysXIncludes.h	41
Then it gives the following errors:
Severity	Code	Description	Project	File	Line	Suppression State
Error	C2232	‘->TUniquePtr<FPhysicsMaterialHandle,TDefaultDelete>::IsValid’: left operand has ‘class’ type, use ‘.’	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	103	
Error	C2232	‘->TUniquePtr<FPhysicsMaterialHandle,TDefaultDelete>::IsValid’: left operand has ‘class’ type, use ‘.’	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	106	
Error	C3668	‘AActor::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\GameFramework\Actor.h	2912	
Error	C3668	‘AActor::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\GameFramework\Actor.h	2912	
Error	C3861	‘CreateMaterial’: identifier not found	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	105	
Error	C2065	‘FAsyncPreRegisterDDCRequest’: undeclared identifier	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\World.h	1649	
Error	C2065	‘FAsyncPreRegisterDDCRequest’: undeclared identifier	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\World.h	1649	
Error	C2504	‘FChaosEngineInterface’: base class undefined	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Public\Physics\PhysicsInterfacePhysX.h	173	
Error	C2504	‘FChaosEngineInterface’: base class undefined	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Public\Physics\PhysicsInterfacePhysX.h	173	
Error	C2653	‘FChaosEngineInterface’: is not a class or namespace name	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	92	
Error	C2653	‘FChaosEngineInterface’: is not a class or namespace name	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	105	
Error	C2653	‘FChaosEngineInterface’: is not a class or namespace name	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	108	
Error	C2653	‘FChaosEngineInterface’: is not a class or namespace name	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	109	
Error	C2582	‘operator =’ function is unavailable in ‘FPhysicsMaterialHandle_PhysX’	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	105	
Error	C3861	‘ReleaseMaterial’: identifier not found	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	92	
Error	C3861	‘SetUserData’: identifier not found	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	108	
Error	C2923	‘TSharedPtr’: ‘FAsyncPreRegisterDDCRequest’ is not a valid template type argument for parameter ‘ObjectType’	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\World.h	1649	
Error	C2923	‘TSharedPtr’: ‘FAsyncPreRegisterDDCRequest’ is not a valid template type argument for parameter ‘ObjectType’	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\World.h	1649	
Error	C2976	‘TSharedPtr’: too few template arguments	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\World.h	1649	
Error	C2976	‘TSharedPtr’: too few template arguments	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\World.h	1649	
Error	C3203	‘TSharedPtr’: unspecialized class template can’t be used as a template argument for template parameter ‘InElementType’, expected a real type	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\World.h	1649	
Error	C3203	‘TSharedPtr’: unspecialized class template can’t be used as a template argument for template parameter ‘InElementType’, expected a real type	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\World.h	1649	
Error	C3668	‘UActorComponent::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Components\ActorComponent.h	375	
Error	C3668	‘UActorComponent::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Components\ActorComponent.h	375	
Error	C3668	‘UAnimInstance::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Animation\AnimInstance.h	1285	
Error	C3668	‘UAnimNotify::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Animation\AnimNotifies\AnimNotify.h	94	
Error	C3668	‘UCurveBase::PostEditChangeProperty’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Curves\CurveBase.h	82	
Error	C3668	‘UCurveBase::PostEditChangeProperty’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Curves\CurveBase.h	82	
Error	C3668	‘ULevel::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\Level.h	757	
Error	C3668	‘ULevel::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\Level.h	757	
Error	C3668	‘ULocalPlayer::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\LocalPlayer.h	277	
Error	C3668	‘UNetConnection::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\NetConnection.h	814	
Error	C3668	‘UNetDriver::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\NetDriver.h	1486	
Error	C3861	‘UpdateMaterial’: identifier not found	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	109	
Error	C3668	‘USoundEffectSourcePresetChain::PostEditChangeProperty’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Sound\SoundEffectSource.h	62	
Error	C3668	‘USoundEffectSourcePresetChain::PostEditChangeProperty’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Sound\SoundEffectSource.h	62	
Error	C3668	‘UWorld::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\World.h	2563	
Error	C3668	‘UWorld::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Classes\Engine\World.h	2563	
Error	C3668	‘UWorldSubsystem::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Public\Subsystems\WorldSubsystem.h	24	
Error	C3668	‘UWorldSubsystem::GetWorld’: method with override specifier ‘override’ did not override any base class methods	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\Engine\Public\Subsystems\WorldSubsystem.h	24	
Error	C2664	‘void FChaosEngineInterface::CreateActor(const FActorCreationParams &,FPhysicsActorHandle &)’: cannot convert argument 2 from ‘Chaos::TGeometryParticle<float,3> *’ to ‘FPhysicsActorHandle &’	HeadlessChaos	C:\OPT\UnrealEngine\Engine\Source\Programs\HeadlessChaos\Private\HeadlessChaosTestPhysicsScene.cpp	1377	
Error	C2664	‘void FChaosScene::AddActorsToScene_AssumesLocked(TArray<FSingleParticlePhysicsProxy *,FDefaultAllocator> &,const bool)’: cannot convert argument 1 from ‘TArray<Chaos::FGeometryParticle *,FDefaultAllocator>’ to ‘TArray<FSingleParticlePhysicsProxy *,FDefaultAllocator> &’	HeadlessChaos	C:\OPT\UnrealEngine\Engine\Source\Programs\HeadlessChaos\Private\HeadlessChaosTestPhysicsScene.cpp	1395	
Error	C1083	Cannot open include file: ‘ShaderCompiler.h’: No such file or directory	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\NetworkFileSystem\Public\INetworkFileSystemModule.h	7	
Error	C1083	Cannot open include file: ‘TextureResource.h’: No such file or directory	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\SlateNullRenderer\Private\SlateNullRendererModule.cpp	12	
Error	MSB3073	The command “…\Build\BatchFiles\Build.bat HeadlessChaos Win64 Development -WaitMutex -FromMsBuild” exited with code 6.	HeadlessChaos	C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Microsoft\VC\v160\Microsoft.MakeFile.Targets	46	
Error	MSB3073	The command “…\Build\BatchFiles\Build.bat UnrealFileServer Win64 Development -WaitMutex -FromMsBuild” exited with code 6.	UnrealFileServer	C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Microsoft\VC\v160\Microsoft.MakeFile.Targets	46	
Error	C2027	use of undefined type ‘FPhysicsMaterialHandle_PhysX’	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	103	
Error	C2027	use of undefined type ‘FPhysicsMaterialHandle_PhysX’	UnrealFileServer	C:\OPT\UnrealEngine\Engine\Source\Runtime\PhysicsCore\Private\PhysicalMaterial.cpp	106




 4.26 was fine.
  4.26 was fine.