I have the same issue as the OP
Animation speed in NG has never seemed to playback at the rate set in the bottom right of the interface (it was fine on pre NG versions)
This isn’t affected by the program running for a time, it just doesn’t seem to work as expected.
I ran into this problem in 2019/20 when trying to animation some rapid VFX that relied on visuals alternating between frames.
To test, set an animation speed of 50FPS. Create 50 blank animation frames. Fill one or more consecutive frames with another color. playback and time the interval between flashes with a stopwatch.
note: the “50” in the test could be anything, but the number of frames must be a multiple of the frame rate (using 250 frames @50FPS and dividing the stopwatch reading by 5 would give a more precise result in theory)
What actually seems to be happening is that the playback is only restricted to a few preset playback speeds and I cannot achieve anything that resembles 50 or 60 FPS playback speed.
Both of these issues have occurred on 5 different machines with both windows 7 and 10.
BTW: I have had the Stuttering problems described above when I have loaded an old .fli/flc file. I don’t think this is related to the same issue.
Thanks Jan. Hope you’re well
edit I mention using FPS to test. the same occurs when using Milliseconds