Looks like it’s also related to the intervals between actions being too short and/or the actions being too slow (opposite of the problem I described above) - here are the numbers for the Handy: Some guides and formulas you can use when scripting for the Handy using OFS
A tool like this might help: Fun Expander 2.5.2 - Video converter with ffmpeg to i-frames added [Updated 2022-04-11]
It looks like some software to play funscripts can manage these issues without causing the Handy to stop. e.g. HandyControl 1.2.3 (28.11.2021) - Added Support for Pyro (Remote Control)