A.15 WCAG 2.1 Success Criterion 2.3.2 − Three Flashes
Ensure there is nothing on a website that "flashes" for more than three times per second irrespective of its size. Otherwise, this may cause problems for people who suffer from epilepsy.
Before Rectification
In this example, the traffic light image is flashing too fast and is large in size. This can cause seizures.
After Rectification
It is better to replace flashing content with static content that does not change.
WCAG 2.1 Reference:
https://www.w3.org/WAI/WCAG21/Understanding/three-flashes