I am having the same issue.
Yesterday i tried the following and the amount of disconnects got reduced drasticly.
- Removed my secondary monitor
- Closed discord
None of the two solutions is in my opinion viable, but it seems to me that diablo cant handle processes from the second screen.
Having discord open while using one monitor still gave alot of disconnect.
Maybe one of you can use the info to get closer to a solution. Hope it helps