'No breakpoints hit when debugging Qt subdir projects

I've just spent the last two weeks trying to debug my test Qt subdirs project and as various similar questions both here and elsewhere have stated any breakpoints placed in the main project (TEMPLATE = app) will be hit, but nothing works in any sub-projects/library projects (TEMPLATE = lib). Before I start posting any details I'd like to know; am I missing something obvious or is it really not possible to debug sub-projects in Qt Creator?



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