As far as I can see these are volume snapshots, right? You need to check if the snapshots on XenServer are part of a chain. Are you familiar with vhd-util in XenServer cli?
What is your value of snapshot.delta.max in global settings?
We have one situation on CloudStack and Xen with Snapshot, see print attached,
we have many snapshot showing on XenServer but on ACS this snapshot not exist
I can delete manual via Xen this snapshots ?? what happen for generate all this snaphost
without register on ACS ?
Att / Regards