Interesting, I'll have to wait to see if the same pattern happens here. Backup went fine yesterday, and this night (as usual). Only occured on one (1) VM for me, so far.

- I did also notice a DRS vMotion (auto) occured on the VM earlier the same day (some hours before I got the snapshot/locking issues).

Q: Maybe you could check, if same pattern occured in your environment; e.g. vMotions/changes on the VM before snapshot issues occured? If so, lowering the DRS threshold could also help "slow down" the occurence (not a permanent solution, but the impact/frequency may be reduced).

I'm also running ESXi 7.0.2 build-17867351, in a 4-node vSAN cluster.

Q: Are you also running vSAN, or is this regular VMFS/NFS datastore?