On certain DVDs, the Truetheater Motion feature does not work while deinterlacing is enabled. In other words, there is no noticeable motion-smoothing unless deinterlacing is manually disabled, at which point the motion is smoothed, but interlacing artifacts make the video unwatchable. When deinterlacing is re-enabled, motion-smoothing ceases again. This happens regardless of the deinterlacing method.

I have not been able to determine a pattern between which DVDs work and which do not work, so as an example: Classic Media's "Godzilla Raids Again" features WORKING Truetheater Motion, while Shout! Factory's "The Transformers: The Complete First Season" DOES NOT unless deinterlacing is disabled. The only steps required to reproduce this issue are to begin playback, turn Truetheater Motion on, and see if it's working or not. If not, disable deinterlacing and Motion will work. The problem is that both will not work at the same time.

There is no error message displayed, and since the problem can only be seen in motion, I can't provide a relevant image. I've attached my DxDiag file on the offchance that it may be helpful.