OK, here is a sample *sln.
Open the SLN in slickedit.
In the Files toolbar, Project Tab, double click "Ex1.cs".
It opens without coloring -- it opens as PlainText.
- This is RC1, Migrated from 25.0.2
- It does not happen with 25.0.2
- It does not happen with a clean configuration.
- I made fresh copies of these files in new directories, so "perfile" shouldn't be confusing things.