Just wanted to add one tip that you may be unaware of. From what I've read, it is a good idea to have one repeater for every 6-8 zigbee end-devices like the Xiaomi Mijia/Aqara sensors. Also, both the Tradfri outlet and the USB repeater function as zigbee repeaters for Aqara/Mijia sensors.
FWIW, I have a bunch of Xiaomi devices (including "original" mijia motion sensors) and no issues whatsoever with connectivity and no dedicated repeaters at all. I'm using Gledopto zigbee lamps and since they are powered they are acting as repeaters and seem to be doing a fine job with all the Xiaomi kit.
The one with the M on top(mejia) gave me issues, the 2 other aqara sensors I'm still using and they work fine.
I only have xiaomi compatible routers and have 4 xbees to boost zigbee everywhere.
Maybe my mejia motion sensor is bad, but for me, it's a fail, would not stay connected
Could be. My Mijia motion sensors are the only ones that will stay paired to HE! Try a factory reset and new battery too. It seems like battery level might be a factor with the check-in frequency.