Question I can only build once per editor version.

Hello Unity users and Unity Team.

Every time I try to build for a second time I get this error.
To build again I have to a) Update Unity editor or b) delete all except for assets and proj-sett, which does a reimport.
After that I can only build once and the build takes literally hours instead of 30 seconds (Compiling gazillion shaders for some reason).

It has been like that since a few months ago and it kills the joy of creating my passion project.

What could cause this?

Thank you in advance,
Yossi.

Edit: omg... after 5 months of agony and no way to iterate builds the thing that resolved it was going from mono to IL2CPP try to build, get the error where I don't have VS2017, Go back to mono and I can build again...
Let's hope it stays that way...