why would my OneDrive suddenly be processing over 40,000 changes?

Same for me.

Started today. 100s of thousands of files. Nothing more to add, really.

I’m seeing the same issue. Suddenly, OD started reporting that it needs to process over 200,000 changes. This is the second time it’s happened in the past two to three weeks.

Hello Liam,

Thanks for the feedback but in my case this relinking the Onedrive App as a serious consequence. I had to do that relink once before and it was painful process to get through.

The reason is that also my Synology NAS uses MS Onedrive (Cloud Backup app). It is syncing encrypted (selective) NAS files and folders to Onedrive. As I have 1 TB of storage is good use as Cloud backup storage from my home NAS as distaster recovery (e.g. house burns down).

For the Onedrive App on my laptop I have excluded specific the NAS backup folder to be synced and of course not allowing all to be download locally back to my humble laptop.

The moment, I do the relinking, as you mentioned and I know too, OneDrive will also first scan all online folders and files. Including the NAS ones. These are of course an enormous amount of files. Which actually don't need to be even shown on my laptop's Onedrive. Only in the second stage I can unselect that NAS backup Folder from the Onedrive App on my laptop. Actually I would love you could do that earlier. Or Onedrive would remember in the cloud your previous Onedrive Settings or offer at least to import them.

Was not using Nord VPN or any VPN on the computers we had OneDrive explode on. Also happened on both Windows 10 and 11 and Mac (including different versions of macOS). I think this problem is more widespread than VPNs.

You brought an interesting topic... I also use VPN. Proton VPN.