The server disallows any collection created with ".system." in its name.
https://github.com/mongodb/mongo/blob/r4.4.12/src/mongo/db/ops/insert.cpp#L273

When scan_checked_replset.js operates on system collections, it attempts to create the collection with names such as "admin.dbcheck_backup.system.users.3" which violates the constraint.

We can modify the prefix generated in the scan script to use a different character:

const saveCollPrefix = "dbcheck.";
const backupCollPrefix = "dbcheck_backup.";