Unexplainable Shadows with Workbench Render Engine

Hello,

I have a model of an industrial engine that when rendering with the workbench render engine has some bad shadows. I tried many things that I figured it may have been but it did not help. I tried:

recalculating outside Normals, merging double vertices, checking for creases and marked edges etc. If anybody has any ideal it would be a great help. It does not have this problem with EEVEE. I have uploaded the file here. Only part of the engine model is left by the way in the file. I had to delete most of it to make the file small enough to upload here.

As well I have uploaded a quick render so you can clearly see the odd shadows being produced.

Engine Bad Shadows with Workbench Render.blend (2.4 MB)

Messed with it some more. Decimate geometry removed the guilty parts of the mesh. I believe it was caused by inside faces and normals intersecting through outside faces and such. The model was a mess imported as an obj from grab cad because I didn’t have time to model an engine for the project.

Reduced the geometry in half using decimate without a noticeable change in quality. Next time I will start my project much sooner in advance to model a comparable model taking my time over a long period of time and with cleaner geometry and a lot less geometry!