If you turned off your repeaters during pairing, and then powered them on afterwards, it’s quite likely that the Xiaomi sensors dropped their network connections because 1) they were connected through one of your repeaters or 2) they weren’t connected through a repeater and the mesh network signal strength was too weak due to distance from the hub.
You could try pairing them at a close distance to the hub, wait until the first battery report comes in (which means they made it past the hub’s end device timeout period), and then move them to their intended location, and hope they change over to being connected through a repeater. But if the repeater has an end device timeout shorter than 50 minutes then the Xioami sensors’ connections would be dropped anyhow.
Without a device like an XBee Zigbee module to map your Zigbee network routing, it’s not very easy to know whether Zigbee end devices (like any Xiaomi sensors) are connected through a repeater and what their signal strength is.
Interestingly, it appears that using an XBee module as a repeater is the only solution that works well with Xiaomi devices, if you set the XBee’s end device timeout (known as Child Poll Timeout on an XBee) to be longer than an hour. See this thread for more information: