Seems to be a control rig problem
No handler found for function 'FRigUnit_ControlRigSplineFromPoints::Execute' for VM '/Engine/Transient.RigVM_12'
Perhaps this could be linked to the following error regarding splines and control rig
This also stands out
[2023.11.20-15.51.09:868][272]PackagingResults: Error: Assertion failed: (SourcePin == nullptr) == (TargetPin == nullptr) [File:D:\build\++UE5\Sync\Engine\Plugins\Runtime\RigVM\Source\RigVMDeveloper\Private\RigVMModel\RigVMGraph.cpp]
Seems like some critical pins in the control rig are unplugged causing problems
I’d go into your control rig blueprints and check if they are compiled without errors.