Thank you for contacting Plugable support! Sorry to hear about this issue. I’d be more than happy to assist you.
M1 Macs can only support a single external display through a Thunderbolt 3/USB-C dock such as this. This is due to M1 graphics card limitations that previous Intel Macs did not have. As such, you will be unable to use more than a single display with this dock and your M1.
Please note that this dock does not use DisplayLink technology, so those drivers would not have been able to help in this case.
For the pixilation issue, if only connecting a single display, this should not happen. Reboot your M1 with only one display attached and see if it’s no longer pixelated.
We do make other docks that can support dual displays with an M1 Mac, these docks use DisplayLink USB graphics technology to work around the M1 limitations. It would also be possible to keep the current dock, but add a DisplayLink USB graphics adapter to one of the dock’s USB ports to enable a second display that way and thus bypassing the non-functional second output of the dock. If you’d like, I can make some possible recommendations.
Please don’t hesitate to let us know of other questions.
Thanks again for contacting Plugable support and best wishes!
Senior Engineer | Product Owner