Hot Reload attempting to build unrelated files

Hello,

I am working on a Monogame project which has many .cs files for game logic but also some .fx files for shaders. For a few months, hot reload has worked as expected. However after opening and editing some .fx files, hot reload now attempts to build those files when applying changes. It does this even though those files are not normally built via any project, and there are no changes to those files. 

This effectively has broken hot reload for my application. I need Rider to not attempt to compile/build those files during hot reload (which it doesn't during the normal build anyway). I have already tried to File > Invalidate Caches.

Any suggestions?