In my attempts to ensure I didn't lose any data after my server stopped running I put 4 x 2 TB SSDs from the server in a QNAP USB3 DAS.
I then backed up my data from my main PC to two of the SSDs using SmartSync Pro, which has been my backup app for years.
It is set up to copy over all new/updated files but ignore Recycle Bin and System Volume Information.
My data is on the D drive at D:\Data if that is relevant.
I left it running, it took much longer than I expected and after it was finished I saw it had managed to convert the relatively small 43 GB of data on the source drive into over 800 GB of data on the destination!
On inspection it seems to have recursively copied the Data directory into itself nearly 20 times and then changed the destination directory name from "DB-JGMAIN" to "Data".
The "desktop.ini" file contains "LocalizedResourceName=Data" which is standard when you tell Windows to keep data elsewhere than in the user directory.
I have used this backup app for donkeys years, it has always copied all files including "desktop.ini" and always been 100% accurate.
I then amended it to exclude "desktop.ini" and it ran perfectly.
So conspiracy theories territory, why on earth did it do this? Has MSFT update Win 10 to take more notice of "desktop.ini"?