That’s exactly why I posted my initial comment here… The issue does exist even though not everyone has noticed/spotted it. We shouldn’t get into discussing whether it actually exists again. 
We’re thinking of ways to debug/tackle this issue in the team.
Awesome, thank you. Please keep us informed 
I’m not claiming the problem doesn’t exist. Just that I haven’t noticed it. And while I’m not hugely worried about a glitch now and then, I do usually notice them I think …
I would welcome if we could focus on the issue as well, meaning looking into a solution and/or making the workaround solution (disabling dirtyregions) viable regarding idle temps.
Also I think the entire community would benefit if the whole dirtyregions vs smartredraw issue is finally clarified.
I’m glad to hear someone is still looking at the subtitle frame-skip issue. I’ve been following this for a while - I think it was probably me who originally uploaded that Avatar clip. 
There’s one other situation where subtitles can cause major problems, and that’s on 4K/60fps material. That may or may not be the same issue, of course. I’ve got a 2 minute clip of “Billy Lynn’s Long Half-Time Walk” which can skip like crazy with subtitles on - you can lose over 300 frames in 2 minutes.
There are two particularly odd aspects to that one. The first is that with subtitles on it skips even where there are no subtitles actually visible on the screen. The second is that it’s strangely non-deterministic - you can play the same clip twice, and it might skip 12 frames the first time and 150 the next.
The lack of reproducibility suggests to me that it’s something quite low level that’s causing the issue, maybe even a hardware issue - fluctuating GPU clock speed, maybe.
Anything new on this issue?
I’ve noticed this recently on some 4K HDR files with SRT.
Have you tried the latest 4.9 build?
I’m not pretending to follow the technical details of this discussion, but there have obviously been some recent changes with regard to skipped frames. Using the most recent Matrix test build, my 4K Avatar test clip now plays smoothly, which is a significant improvement - it always used to visibly skip a frame every time a translated-Na’avi subtitle came up.
But 4K/60fps stuff like Billy Lynn’s Long Half-Time Walk or Gemini Man still skips frames quite badly with subtitles turned on - despite the fact that one CPU core is now always pegged at 100%, which it never used to be.
Yes, that’s a major improvement we’ve also noticed due to recent changes that were made.
We’re still working on that.
4.9 stable is around the corner right?
I’ll just wait for stable.
Funny thing though, I don’t remember having any stutter issues with my UHD Remux of Gemini Man with PGS subs.
Yes - it should be ready for mid July as an approximate ETA.