This is discussed at length in the thread about the DTH, so you should just talk to the folks there.
The short answer is that the standard requires that a zigbee Device check in with the hub every 60 minutes or it will be marked as missing. The Xiaomi devices Report right on the edge of that time period, so they are more vulnerable to being dropped.
On top of that, they appear to have difficulty working with many other ZHA repeaters. There are only a few that work well with them.
So the solution for most people has been to find one of the repeaters that does work well and add it where the Xiaomi devices will use it, which helps them report in a more timely fashion.
But ask the people in the following thread (this is a clickable link), as they are the ones with experience: