C-7 here with same issue, cloud backups started failing and reported Zwave backup incomplete. I tried the suggestion in the thread below where someone else started reporting this issue a week ago.
Shutdown hub, remove power, wait 45 seconds, power up hub. Run a manual cloud backup which was successful. BTW, this issue is also wrecking some havoc with the Zwave network, at least for me. I had to repeat the power down procedure a couple more times to get my Zwave network to settle down.
