The moving target that is the OneDrive migration mess continues.
In File Explorer, without me doing anything, I now have a folder (not a shortcut) called Personal-Vault-XXXXX where XXXXX is the name of the computer. This folder has no additional security on it and simply opens when selected. Double U Tee Eff (since MS turns the three letter acronym to **** if I write it). At least in the web client I only have Personal Vault, not a synced copy of Personal Vault-XXXXX confirming that this is a PC issue as implied by the folder name.
Remaining in File Explorer, I still have the usual shortcut called Personal Vault, which when I select it correctly prompts me for MFA and then opens a new File Explorer window with all the sub folders in the vault. Even when unlocked however, it shows the red X (locked).
When I try to delete folder Personal Vault-XXXXX there is a long pause and then a message saying words to the effect of 'there is a problem accessing this folder. Try later'.
The computer has been on all day since rebooting to try and solve the issues. OneDrive reports 'downloading 3.7MB of 3.7MB at 0.0 KB/s' as it has all day. This might be connected with the Personal Vault locking after seconds despite being set to lock after one hour.
I just pray my Personal Vault contents are all still present; since many are confidential, I don't have local backup. I will now download the folders from the web client and see.
What a shambles.
[Edited to add that on a symmetrical gigabit fibre to the home connection with Cat 6 Ethernet from the router to the computer, and with all other network activity paused, the download is running at between 70KB/s and 200 KB/s. Unbelievable. I have 34GB to take a local copy of.]