Well I didn't read that exactly. But after restoring the backups the MongoDB container wouldn't start. The log produces an error like this:
2021-06-25T12:07:32.538+0200 E STORAGE [initandlisten] WiredTiger error (0) [1624615652:538965][1:0x14e9929f5a80], file:WiredTiger.wt, connection: __wt_btree_tree_open, 585: You should confirm that you have opened the database with the correct options including all encryption and compression options Raw: [1624615652:538965][1:0x14e9929f5a80], file:WiredTiger.wt, connection: __wt_btree_tree_open, 585: You should confirm that you have opened the database with the correct options including all encryption and compression options
Reading up on that it seems this happen if you try to use files that was backed up without stopping all writes to the mongod before copying the files. I read that here under Back Up with cp or rsync: (https://docs.mongodb.com/manual/core/backups/) I realize the plugin uses tar? But I suspect the same applies?
So my deduction (which of course may be wrong) is that the MongoDB instance was not shut down or not shut down properly before making the backups resulting in the WiredTiger error. I have only briefly looked in to this though.
I found this: https://medium.com/@imunscarred/repairing-mongodb-when-wiredtiger-wt-file-is-corrupted-9405978751b5
which I plan to read through and try this weekend.