Vastly different results between v2.6.4 and v3.1.6 when using the same settings - am I doing something wrong?

If the suggested changes that @TPX did not help, then you probably have to pull the heavy guns out now.
with interlace source there isn’t much room to play with as far as settings and tweaks goes in TVAI.
on the other hand with Progressive source you got hell a lot of options to play around with.
what you should do (try), is to de-interlace your rip file 1st externally with “Hybrid” free tool.
I would personally also export the rip into a"lessless" format if you got the storage, that way you feed TVAI the maximum quality source for it to work with.
Once you de-interlaced your rip, I would suggest you give @TomaszW upscaling presets a try and see which one works best for you. That would save you tons of time trying to tweak your settings by yourself with endless trail and error.

  1. de-Interlace/lossless using Hybrid
  2. TomaszW presets
  3. Topaz Video AI community support forum

P.S. if you come across on any issues with either of process (de-interlace or TomaszW presets), do not post those issues here in this thread, but post them as a reply on the original post (the links i provided you). also any issues that are not a bug, in general with TVAI, don’t post them here, but in the community forum (link provided above), there you will get much more attention as people monitor that forum much more then this one. besides the fact that it is the more appropriate place to post general issues with TVAI.

Good luck :slight_smile: