I had observed this problem when playing video file via the VLC app on the PPMax. There would be random stutter / jerk / lost frames for a fraction of a second. There is no break in audio. Only the image suddenly jumps a fraction of a second forward. Randomly. Attached below is a sample video. Observe the stutter / jerk / lost frames at 4 seconds. (Note - ignore the resolution of the video because I had to downscale it for a smaller file size for uploading here.)
It can happen randomly regardless of whether the file is played from internal memory, microSD card or USB 3 harddisk.
I discovered that the problem seems to have stopped after I turned OFF the Auto Keystone in PPMax settings. I am not sure. I will need to do more tests for longer periods to confirm.
If you have this issue of random stuttering, perhaps you can test if turning OFF the Auto Keystone will work for you. Do share your findings.