I ended up returning the XT8 and am back to the much more reliable AC86U/AC68U AiMesh combo.
I'm disappointed as I really wanted the XT8 to work - it seemed ideal for my purposes where I cannot use wired backhaul, so I had high hopes for the dedicated 5Ghz wireless backhaul. Looks like I'll be...
I've had a similar issue with the XT8. Rebooting the nodes brings back 5GHz backhaul, but after a while it reverts nack to a 'weak' signal and 2.4GHz. I'm very close to just returning my units, after tweaking for a few weeks to get the best performance.
The XT8 is a step down from my older...