RPi4, 8Gb - Dual Monitor interferes with Video

Currently running the 64bit version of Ubuntu Mate on an overclocked 8gb model Raspberry Pi 4.

Whenever I have two 1080p monitors connected to the Raspberry Pi, whether in Chrome or Firefox, the video struggles to load (if it loads at all).

However, browser based video loads without issue when only one monitor is connected to the Raspberry Pi.

I had the same experience.
With dual monitors, system monitor show the CPU load is about 20%, but the network downloading is extremely slow in the log.
I believe this is a network-related bug.