Runtime fatal error - possibly CLR bug

I ran into this working on a Dotnet Core project. I deleted the binaries and rebuilt, this fixed it for me. Simply doing a Clean and Build or just Rebuild had no effect.

It's most likely not a CLR bug, but probably a Heisenbug. We can't really say what's causing it, though, without seeing your code.

Try turning on Managed Debugging Assistants to figure out if some error or access violation is being suppressed.