Premiere 2015 has been pretty buggy for me too. I’ve spent many chat sessions with Adobe support the last few weeks/months. A temporary solution(until they fix this $h!t) is to basically do a clean uninstall /reinstall using the Adobe cloud app.
If you’re hesitant to do it, because I was, they also suggested renaming all Adobe folders to “old Adobe” and relaunch Premiere. This is essentially the equivalent of deleting all your preferences. I’m referring to the folders inside of application support, documents, preferences etc… Also make sure you have updated all your software both Mac and Adobe. I would also remove any add on plugins too if you have them.
It’s messed up, but that’s the only way I could get back to sane editing. These latest updates have been killing my workflow as well. Too bad we can’t get reimbursed for all the lost time.
Any further help needed should come from Adobe support. I hope that by making them aware of these issues, they will get around to fixing them. Good luck.