DisplayPort monitor goes dark every few minutes and then recovers a few minutes later

I have two monitors - a BENQ 27" 4K DisplayPort monitor and an old LG 22" 2K HDMI monitor connected to my plugable dock.

Unlike other similar reports, Windows does not see the display go away (i.e., the windows on the BENQ monitor don’t get ‘pushed’ onto the LG), so my large monitor is all but unusable. It seems this display-flickering issue is widespread and I have repeatedly deleted and reinstalled the displaylink drivers to no effect. What solution options am I missing?