I took a look at the manual entry for compilation-mode, which contains:

       Sometimes ‘compilation-error-regexp-alist’ doesn't correctly
    determine the filename that is the source of the error.  Use user option
    ‘compilation-transform-file-match-alist’ to make any necessary
    adjustments, such as adding or changing a directory component, or even
    considering certain compiler messages not error messages at all.

This suggests a surgical fix (attached) that addresses the cases of the
bug that I had been able to reproduce.  Perhaps Johann can check if it
addresses his cases, too.