As noted in THIS THREAD, citations aren't being added to a bibliography document when using the "add from clippings" tool. I am running 7.5.0.0031 on macOS 10.12.3.
I rarely use this feature, and I believe a case may have already been created. If so, I hope it is a regression and not a longstanding unfixed bug! 
EDIT: The issue in the other thread may be unrelated, after reading Graham's post.