for the delete snopshot issue there are many situation in fact.
one host just support 32 snopshots and need delete the last one every time.
1、check the VM have migrate or not. if migrate need check the disk have bind or not.
2、in some situation the database record not the same between the master and slave node. need restart the vnad service.
3、check the snapshot is in use or not. if in use with some service need delate will modify the database.
...
for snapshot delete issue need check the environemnt and the error info to analysis.
thanks