I found some facts that prove that the problem is in the brain's neural adaptation to flickering, here is link ( 2 and 3 page ). This man change a lot of phones without success, and here is results of his electroencephalography. Also, @jen research could be userful -> https://www.flickersense.org/testing-leds-and-screens
To sum up: people get new flickering device and can't use it, only switching back to old one, helps
I think, using any visual device = adapting to its flickering. Apparently, the "previous" device was very stressful for the brain, because it had adapted so deeply to it, and adaptations to new devices cause new stress for existy stressy brain