Don't forget that completely deleting the cache files can solve a number of stability and playback issues, especially after upgrading to a new version. Changes in the software mean Premiere may need different cache files, so this is a necessary step (it also can solve some weird pop-up playback issues unrelated to upgrading). When you upgrade versions, follow the recommended steps for deleting all your cache files. Look up the procedure in Help (I think the instructions are also in the Media Cache tab in Preferences) - it involves opening Premiere Pro without opening a project, then going to Preferences > Media Cache.
o2 ideas - Birmingham, AL
iMac Retina 5k, 27-inch, 2017
4.2 GHz i7, 32GB RAM, Radeon Pro 580 8GB
G-Speed Studio TB-2 12TB RAID-5