Two backup programs, diff and log out of sync
Differential backups are attached to the Full. If your other backup tool takes a full, it's normal that you cannot restore your diff without that full.
You should not use 2 different backup tool in parallel. If you really need to, then you can check if it's possible to specify the &quot;copy_only&quot; option for the backup in CommVault (so your native backup will remains the &quot;official&quot; backups).
If it's not possible, you could then do only full (with copy only) on your side. Of course, if the database are big, this mean bigger backup and longer time to restore.
Maybe you should address the problem at the source. It seems to me that what you really need is permission in CommVault to be able to run restore from that tool.