Unraid docker slowing down router

I installed the xibo docker in unraid (xibo-cms) through Community Applications, but after a few hours of running, my router gets really slow, and my internet speed falls down to 100/100 megabit.

Stopping the docker makes my router instantly return to normal, and my internet speed is back to the 500/500 megabit it should be.

What can it be doing, which could cause this?