I am currently investigating a strange terrain collision issue affecting a blueprint-only project. I have posted details on that issue on the UE4 answerhub here but I believe the issue can be tracked back to the FMOD integration.
I decided to create a fresh project (First Person BP) and add the FMOD plugin. I did not add any FMOD banks or build an FMOD project at all; just created an empty FMOD folder in the Content directory. I Ran the normal initialisation (Help > FMOD Validation), and then tried to compile the project to a standalone build, and I get this error:
Assertion failed: Local1.IsValid() && !Local1.ContainsNaN() [File:D:/Build/++UE4/Sync/Engine/Source/Runtime/Engine/Private/PhysicsEngine/ConstraintInstance.cpp] [Line: 359]
Once I disable the FMOD plugin, it compiles just fine.
Going back to my original project issue of strange terrain collision (again, see this post for more details on that), I made a copy of my original project, removed the FMOD plugin and all references to it, and the terrain bug goes away.
For some reason the 4.23 integration is interfering with UE4’s physics / collision system.
I am using UE4 4.23 and FMOD 2.00.05, and VS 2019