Failing to package a project in UE 4.26, is claiming an InterfaceBP must be a UCLASS?

Hoping this is correct place to post. I’m having a rough time trying to package a VR project (began as the VR basics starter project). There have been a few issues that may have contributed to this problem, though not 100% sure they are even related.

The main problem is that the cook part will now complete but when it begins to build, it fails pretty quickly spitting an error that;

UATHelper: Packaging (Windows (64-bit)): D:/UE4/MMORPG_CraftingSIM/VRMMMORPG_CraftSim/Intermediate/Plugins/NativizedAssets/Windows/Game/Source/NativizedAssets/Public/MotionControllerPawn__pf563933975.h(630) : Error: Unrecognized type ‘IPickupActorInterface_C’ (in expression TScriptInterface<IPickupActorInterface_C>) - type must be a UCLASS

UATHelper: Packaging (Windows (64-bit)): AutomationTool exiting with ExitCode=6 (6)
UATHelper: Packaging (Windows (64-bit)): BUILD FAILED
PackagingResults: Error: Unknown Error

I only use blueprints, I haven’t messed with anything like that. The actor interface is one that came stock standard with the project to allow players to pick up and drop stuff. I did add two more functions to the class (with one including a Struct Variable I have created as input), however I don’t see how that would affect it.

To understand some things that may have affected the project a quick recap of timeline events include;

  • I had managed to package this project once just to see what would happen and it had worked
  • Later after a few months of work I had accidentally moved the engine files for 4.26 from its location in C: to another drive and had to reinstall the engine
  • Continued working for a time with no issues (no attempts to package again since previous)
  • Tried to package again, was failing outright (re-validated the engine files with the Epic launcher, it had to download more stuff do more stuff etc)
  • Packaging started to work but would fail because of some redistribute 2019 C++ thing (installed it and was now passing this error)
  • Now it fails after the build command part is starting, saying the PickupActorInterface has to be a UClass

After another lead I tried visiting every actor referenced by the class, or using it I guess, making sure none of them had anything going on in the construction script (by simply un-linking a few lines of BP from two BP actors, but still nothing.

Is there anything else I could add to help find an answer (resisted dumping a giant output log as I think that one line is where things go properly wrong).