There is a bug in Youtube's AI filter that is causing some videos to flicker. The content creator have no idea that is happening and no way to opt out. If you have Epilepsy it is recommended that you watch out for these situations
Also as content creators dont know this may be happening, if you find these issues you should try to contact the respective content creator and let them know this is happening on your specific device. Again, its so random it may only happen on some devices