https://bugs.winehq.org/show_bug.cgi?id=52143
--- Comment #1 from Esme Povirk madewokherd@gmail.com --- FIXME messages are not bugs, just hints about things that might cause problems.
Those messages don't necessarily indicate a problem with mscoree, but knowing it's used may be a useful hint. You could check whether that's the component at fault by installing native .NET Framework. Alternatively, setting WINE_MONO_TRACE=x when running without native .NET Framework might print some exceptions that make the cause more obvious.