Unable to add certain .cake files to a solution folder

[CharliePoole]

Has anyone run into this or have any ideas?

I have a number of cake scripts in a cake subdirectory and most of them are visible in a corresponding VS2022 solution folder.

A few scripts can't be added and give rise to the message "The currently open solution file, user options file and project files cannot be added as solution items." The message makes on sense, since they are just text files with the .cake extension.

I have ruled out the possibility of the file's codepage causing the error - it's the same as those that work and I can't find anything inside the files, which might trick VS into thinking it is a solution file, etc.

Any ideas?