OK - I have a newer version, and I think I’ve figured out how the freeze happens (it is still happening, but it seems more clear WHY).
Update Channel: dev
OS Platform: Linux
OS Release: 4.4.0-93-generic
OS Architecture: x64
It seems that VIDEOS in tabs which are being previewed during pointer movement across tab headers are loading into memory, even after the pointer moves out. There is a big pause while the video loads. Move the cursor across several tab headers, and there can be a big freeze.
Thus, previewed tabs need to STOP loading videos and monster images if the pointer moves out of the corresponding header to a NEW header. Not sure this can be done, but that seems to be the root of the issue.
This correlates with the pages which have caused the most problems - things like Twitter, Google image searches, pages linked from video searches, pages with LONG comment threads, etc.