After enjoying TBT3-UDZ for a while and am generally very happy about it, I also noticed an annoying but quite occasional issue.
It looks like that every about 2 to 12 hours, the dock will disconnect one of USB or display for a very short moment, probably less than 0.1 seconds. I will either see display went blank for a very short moment, or Ethernet gets disconnected, and / or just Windows makes sound notifying device removed and then immediately added.
The issue itself is fine but sometimes because it gets reconnected too fast, system is not handling it properly. Ethernet will sometimes not working with error shown as “same named device already exists” and refuses to work until I disconnect and reconnect manually. USB connected hard drive might not be mountable for similar reason. Display might not get initialized properly that it defaults to a very low resolution. All these issues happens on even more rare occurrences, about once one or two days. And all fixable by just disconnect and reconnect manually.
I have the same issue with two different units of TBT3-UDZ and on two different laptops, one ThinkPad T470 and one T480. They are in different locations so most connected devices are different too. All driver, firmware, and OS are up to date.