A little over a year ago I bought 4 of the TUYA Mini USB Repeaters. At first they seemed to work well and I gave then a shout out here. A couple of months ago one died without too much fanfare and I replaced it with a generica TUYA equivalent.
A few days ago I was trying to pair an XBEE to my C-8 Pro and it just would not go. I tried all kinds of things like updating the Hub, moving the Hub, changing my WiFi channels, bypassing Zigbee 3.0 repeaters, pairing in the open. etc.
Eventually I decided to try changing my Hub Zigbee channel. I didn't change anything with regards to the XBEE but now many of my other devices did not re-connect to the new channel and attempting to pair them manually resulted in many of the same issues I had previously had with the XBEE. Sometime I would get a device paired up to the network again and it would work, but a few minutes later it would stop working. All very frustrating.
By looking at what was working and what was not I was able to narrow it down to one of the TUYA mini USB repeaters. I did this by figuring out which devices were not working and using the Zigbee Monitor Driver to determine that they were all children of one particular repeater. The repeater "worked " in the sense that it was part of the network and it's packet count incremented, but it's overall presence was extremely detrimental.
Once I removed the offending device everything started slowly started working again. The pairing process is now back to normal and I was able to pair my XBEE on the first attempt along with a few other orphaned devices.
Bottom line is if you have any of these TUYA Mini USB Repeaters on your network there is a very good chance you have a ticking time bomb. If you are having pairing issues then unplugging those would be one of the first things I would try.
For some extra info I have 9 repeaters on my network, 4 of those were the Tuya Mini Repeaters. However, about 95% of my devices would select one of these as their parent device, presumably because they have a stronger signal. I suspect this also results in these devices being first responders to pairing requests.
Note: I tried the option to pair ignoring Zigbee 3.0 repeaters many times and it did not improve the situation. The implication being that choosing that setting does not bypass these particular repeaters.
I'm sure there is a lot of variability in these mini repeaters so this is just an FYI. Mine were bought directly from China, I think they were about $10 each.
On the front of mine is nothing but a tiny hole where the blue power\status LED shines through. On the back it says Model: RP-ZB001.
I have not figured out a replacement but I am going to buy a couple of the IKEA plugs to see how they perform and see if they would be a decent substitute because they are pretty cheap. I have some WiFi ones I'd like to replace anyway.
I have also thought about the Sonoff dongles with the external antenna. I think the signal would be strong but they are a little obtrusive.
I have had good luck with the Third Reality Smart Plugs as repeaters. I saw where you said you wanted to replace some WiFi plugs. Probably the second best repeater I have on my network. If you don't need power metering you can get a pack of 4 on Amazon for $31.
If you need an MMWave sensor the Linptech sensor works well is by far the best repeater I have.
Now I am basing this off using the Zigbee Map application from HPM.
This is how mine are, I have two. Your comment made me check and I discovered one of them had fallen off and needed to be re-paired. (Thanks for posting. ) It's on a C7. I had recently moved several other repeaters around so it may have been that it couldn't keep up w/the changes.
Never had any issues from them that I'm aware of from them, but as always this stuff is very YMMV.
Wow, thanks! I have 2 of those in service, with no issues yet.*
I just got a good deal on 2 Aeotec Zigbee repeaters, but haven't put them into service yet. This may prompt me to go ahead and get one in place to see how I like them. Any thoughts on the Aeotecs before I find out on my own?
Not a lot of dedicated repeaters out there, especially available as current/new stock. Any other recommendations? I may end up with some smart outlets.
*No mesh issues. I have had trouble with a couple of them falling apart. I mentioned that I got a decent deal on the Aeotec repeaters. While I don't think that deal will be repeatable, the Aeotecs I do have are probably comparable to the Tuyas in cost/unit just because of the failure rate of the Tuyas.
I have a few Aeotec Zi's... They are indeed solid repeaters (whenever I bother to check my zigbee map - which is not often).
I got a decent deal on them at some point, so figured why not. Aeotec stuff has always been solid & reliable for me, but it's oddly expensive (in general) so it isn't typically the first vendor I go to for a new device.
When those plugs came out I picked up several to use a repeaters. In most cases there was nothing plugged into them. After about a year I lost two of them. The relay would keep clicking even though nothing was controlling the outlet. The remaining ones have been in place for a few years but I am in the process of dismantling the mesh (unrelated).
Now my goto repeaters are the Inovelli Blue Series switches and some relatively inexpensive outlets ordered from Amazon.
Any repeater can fail in the same way. There's nothing special about the Tuya repeaters that make them especially prone stochastic failure. FWIW, I have had this happen with Ikea plugs, Ikea repeaters, and Peanut plugs. I also have 8 TuYa repeaters that haven't failed yet.
What is needed in this situation is the ability to do the diagnosis that @garyjmilne did. zigbee2mqtt makes it easy. And Hubitat is definitely in the process of getting there.
What was a little different was that I had a 50% failure rate in a little over a year. But probably more importantly was that these seem to over power my existing repeaters. At the time I had 32 devices, 4 Mini USB repeaters, 5 other repeaters plus a Hub and almost all non-repeating devices would end up being children of the mini-usb repeaters.
This is an old screenshot and shows 11 children on one of these devices, even when geographically it makes no sense. The Office Left (non-repeating bulb) has to pass 4 closer repeaters to get to this particular one and then end up with an LQI of 58 and was somewhat unreliable.
The failure really brought this to my attention but now that I have eliminated them from my network entirely the end devices are generally attaching to the physically closest repeaters.
One thing I should add for people that know a little less about Zigbee is that a child node ONLY communicates through it's parent. You can have the greatest Zigbee mesh with dozens of routes, but the first hop is always to the parent. So, the selection of a parent repeater is very important.
With the eliminated TUYA mini USB repeaters my Office Right bulb (and left) both connect to my XBEE which is also in the office and with an LQI of 255.
From there the XBEE has 9 possible routes.
) It's on a C7. I had recently moved several other repeaters around so it may have been that it couldn't keep up w/the changes. 
