We constantly have this issue every 4-6 weeks with the appliance.
Suddenly the inventory is wrong at the vspere webclient. But only there, the standard client still works with correct inventory.
But also VDP stops working (error = host is in a state which prevents creating snapshots). Normal snapshots still work.
This usually happens when restarting the vcenter appliance after some weeks. Sometimes after vmotion of vcenter.
Our workaround:
1. rename vcenter to vcenter-old (with standard client)
2. clone vcenter-old to another host as vcenter
3. shutdown vcenter-old
4. powerup vcenter
5. if everything works delete vcenter-old and reconfigure VDP to backup the new appliance.