This continues to happen to me (also Surface Book 3 to Dock 2), but not only when computer sleeps. I will be using the computer when one (or both) of the monitors will start to glitch or go black. Sometimes when the monitor goes black, I wait about 10 seconds and it comes back on. When it glitches, I have to disconnect/reconnect the Dock 2. Also, frequently, when I wake the computer from sleep one of the monitors is glitching.
This is occurring on both home and work setup which have the same configuration. The PC is the same one in both cases, but based on the number of issues in this forum it seems most likely that the issue is with the Dock 2.