i found a solution. disable hardware acceleration decoding from preferences and restart Premiere

Yes, same here. Any clip that gets a speed ramp / time remapping effect causes the app to crash or glitch out to the point of crashing. Please fix Adobe!!!

I´m have same problem too!!! Please adobe!! Fix!

"When we use time remapping the clip we have used it on has a straight meltdown. It then decides itself what it will do in playback. It might freeze on a frame, it might stutter through some of the footage, but what it wont do is play correctly. You can scrub through it see where the effect lands, but you cant play it. You render it, to no avail. This is truly messing up the work flow. Please Adobe fix this with haste!!"

Same here any speed ramp over 100% is choppy playback really struggling to complete my edit! had this problem with my last film, updated to the latest version of PP and it's STILL there! Can't get any work done i rely on speed ramping so much for my project, Please fix asap!

Same issue!! Please FIX!!

This is bad.Same issue on 14.0.1. Cant find a work around for this one.

Please Adobe I bouht a supercomputer for edit in 4k, and now i can't use a basic feature as speed ramps! this is absurd

I'm encountering this with H265 videos especially shots from iPhone 60fps. My temporary solution is to make a proxy in H264.

I understand that it can be difficult for Adobe to fix since it involve graphic card debugging. Hope you can fix it soon since it's a work-hampering bug. God speed.

This needs fixed asap, same for me

Same issue for me... On my machine, playback freezes over the portion of the clip where the speed ramp is located and then resumes playback normally once the play-head has passed that portion of the clip.

ADOBE!! PLEASE FIX THIS ASAP!!! YOU'RE KILLING US ALL!!!

Another person adding to this already noted problem...Please Adobe fix this...Just to reiterate what the issue is. When we use time remapping the clip we have used it on has a straight meltdown. It then decides itself what it will do in playback. It might freeze on a frame, it might stutter through some of the footage, but what it wont do is play correctly. You can scrub through it see where the effect lands, but you cant play it. You render it, to no avail. This is truly messing up the work flow. Please Adobe fix this with haste!!

Same issue here, sometimes choppy playback sometimes just a freezed frame.
Very Disappointing.

Yep, 2020 HEVC and MP4 playback is choppy. 2019 playback is much better.

Why does Adobe feel like they need to constantly update things that were working just fine? Totally unacceptable. F*cks with my workflow. F*cks with deadlines. Wastes time. Loses money. I miss the days before CC.

Same thing here

I'm also facing this issue.

I am also having this issue and need it fixed as most of my work requires speed ramping and adjustment!!!

This is unacceptable.
Also, freezing a frame in any clip that has had its speed modified will now give completely unpredictable results..
Generally speaking, you'll just have to close your eyes and pray for the best with every speed change.

Time remapping is stil unreliable after all these years, especially when used it coupled with smooth motion options.
Mostly unusable anyway, since footage skips all over the place in previews.

More:

On one of my recent projects the contents of a 30mins long untouched h264 clip will slide all over the place for absolutlely no reason (i was trying to sync a light switching on with the music; it would be fine in preview, then it would be several seconds late in the export, then every subsequent playback in timeline would have that moment happen at different times, every time).

HEVC support is a mess, with video looping after the first 10 or so seconds forcing me to convert to other formats before editing.

With slightly more articulated projects clips temporarily disappear while dragging them around.

Tons more.
Premiere has become a joke. It's unbelievable the state of this thing in 2020.

I updated it and it quit being choppy