Experiment crashes after about 60 trials

URL of experiment: https://run.pavlovia.org/sheremat/rsvp

Description of the problem:
I have an experiment that displays an RSVP stream with a movie of motion in the background. There are 6 versions of the movie, 3 coherence levels and 2 directions. I have been able to get this to work for about 60 trials (I want ~400 total) but then the experiment crashes. It doesn’t seem to be a specific movie that crashes the experiment or a specific trial (I can sometimes get the output file if I mash the escape key enough).

One possibly related problem is that even when I try to define the movie size in pixels, it displays in normalized units. I don’t know if this is related.

What did you try to make it work?:

I have reset the movie at the beginning of each trial (dotPatch.reset())

I have used stop and seek for the movie at the end of each trial.

I have put the size of the movie as 0.5 and the units as voxels.

What specifically went wrong when you tried that?:

Usually I cannot access the javascript console, but when I can there is no error message.
Include pasted full error message if possible. Sometimes crashes Safari