ref #3054 (comment)

In some projects nothing works at all (colors, completion, ...):

This occurs reliably in a large solution with ~60 projects, but is not reproducible when reduced.

The issue happens in multiple projects, the lowest project is one with 5 dependencies.
If I remove everything except these six projects from the solution, the error stops occurring, even though there should be no change from the view of these projects, so it is impossible for me to provide a reduced reproduction.

For me it looks like something completely unrelated in the solution fucks VS up.

This seems to be related to the up-to-date check:

• If I modify a file and restart VS, stuff works.
• If I build the solution and restart VS, stuff stops working. (Note that before the restart, stuff continues to work even after the build.)

maybe related: #3221

Note: Build always works fine, this is just tooling