As a general rule ChatGPT is not helpful with PsychoPy because its knowledge-base is a couple years old and some things (particularly the MovieStim libraries) have changed in that time. MovieStim3 is an older implementation that uses a different back-end system and has slightly more predictable behavior around certain things like the “isFinished” status.
The catch is that MovieStim3 is bad at restarting playback after hitting the end of a movie file. My recommendation would be to actually load three separate MovieStim3 objects, one for each loop.