After installing my latest PM6 update, I installed the latest version of gstreamer from their website (v1.18) but was not able to see any video thumbnail previews in a contact sheet. I went back to v1.16 through the link on the Camera Bits Forums and was able to view *.MOV files but not *.mp4, which I had been able to do in the past.
Current versions:
Windows 10 2004
PM6 5029
Dave Roth