After new 12.1.1 update I have stuttering playback in preview window - which makes PP CC 2018 practically useless tool for editing.
Old version 12.0 was working perfect - nice and smooth !
I'm working with 4k files on 5k 2016 iMac/external thunderbolt drive/newest system - and the software was flying in this confirguration for months until now.
I have two similar machines both with same results - jerky playpack after installing update !
What happened Adobe ???
What is the exact file format & codec of the footage? If possible, share a sample file with us for investigation. Here are the steps: Share Adobe Creative Cloud files, libraries, and more
I work with various formats and resolutions. In this case it was footage shot on Nikon D5.
But it looks like I solved the problem in the meantime. Playback stuttering occurs only in projects which were created in old version and then converted to the newest one. Project created in new version works OK.
I had to recreate old project in new version, it take some time but it's the only way to get rid of stuttering playback.
Thanks for the investigation & letting us know the status.
Glad you are back on track now.