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
To be fair, they also have little to gain now besides a slight feeling of doing something good but any alternative has to start from somewhere and need to get momentum.