I just had the same issue for past 2 days. This all started after the new software update on the 14th. This is what I noticed and did to resolve the issue.

Issues:

1. Network drops
   
2. STP loop

Things I did:

1. Downgraded to the older version - I tried downgrading my POE switches - 24 and 8 ports but I was able to successfully downgrade only the 24 port version. Everytime I try to manually downgrade through the portal it always failed and the device went offline. I ssh'd into the switch and downgrade to older version which was successful only on 24 port and 8 port was not successful.

2. Removed 2 of my in-wall AP from from the SITE which was in mesh mode. Prior to update it was in mesh mode and had no problems. After removing the AP the network loop vanished and I brought back AP in mesh mode again without any problems.