So there is an issue with my internet that i have been having for a few months now. During random times, my router's PON light will turn off randomly and then turn back on after pulsating for about 2-3 seconds or so. During the time that the PON is off and turning back on, my internet disconnects, and for example if i am playing a game, i cannot move since i have no internet for those 5 seconds that it turns on/off. This makes any game unplayable and its driving me insane. I've contacted the ISP multiple times, they've changed the device to a "new" one, it still does the same exact thing so i don't think its the router. I have a Fiber connection, a ZTE router where the Fiber goes into which is connected into a TP-LINK modem which has the ethernet ports. I have no idea how networking etc works but i hope someone can help me out on some kind of way to fix this issue. I will do my best to provide any information or anything that i can as long as i can have a chance at hoping to fix the issue. Thanks a lot.
Heres a video of what it looks like (video i uploaded):
View: https://youtu.be/vhjoOynsAdM
Heres a video of what it looks like (video i uploaded):