I wish that I had a fix for this, but the game runs differently on different systems. The videos are simple webm files that a Windows system should be able to easily run. Some people have had issues with the Ren'Py engine itself, for example trying to run a game on a laptop that was in battery save mode, or a desktop that the user has put their PC into a low power mode. There are other things that can affect it as well(computer age, other settings, other programs running in the background, etc).
I am sorry that I do not have a better answer. It is frustrating when a game does not run as intended, I have had it happen to me on everything from simple Ren'Py based games to AAA games. If anyone else out there that might know more about this situation and a possible solution, please do not hesitate to let me know, either here or direct message.