Yes it might indeed be hard to reproduce. I have tried both UDP and TCP. Right now I'm using TCP, and it's working... let me see if it ends up being more stable than UDP.
I can try rebooting routers but that would cause angst I would rather avoid. I can move the two of them to the same (unmanaged) switch if it continues to be an issue. That would at least eliminate the wifi mesh as the issue.
Hey just an update. When I switched from UDP to TCP originally I didn't see any improvement but after upgrading both hubs and switching to TCP it seems stable. It may just have been switching from UDP to TCP did not immediately resolve the issue but did after a few min. Or it could have been something that got fixed after 2.2.5.120.
Thank you for an update! I wish I could have taken the credit with software changes 
, but it is most likely switching to TCP that did it. There were other reports that TCP option takes a few minutes to settle down. Also, 2.2.5 has some (minor) hub mesh changes, so having one hub using 2.2.5 and another using 2.2.4 maybe doesn't work as well as having both using 2.2.5. I'll keep an eye out for similar community reports.
Download the Hubitat app
