That's actually an expected behavior, because snapshots are used in a chain where each chain link is active/required.
Best practice for keeping snapshots is to keep them only as long as required, and delete unnecessary snapshots through the Snapshot Manager.
Unless you took the snapshots by intention (manually), check whether "Autoprotect" is enabled for the VM, and consider to disable it. Make regualr backups Instead of using "Autoprotect" (some folks here in the communities call this feature "Autodestruct").
André
