Winclone Error Message when making incremental backup

I have Windows 10 on a Bootcamp partition which I created a clone of successfully. And had done a few incremental backups of also.
Now twice I have gotten a message “Assure that Windows was shut down properly” (which it was using the "Restart in MacOS in the Bootcamp icon) and run CHKDSK (which I did after the first time the error message appeared). But I still got the message again.
I realize that Windows 10 did updates before both times that I attempted the incremental backups. Not sure if that caused this problem. But not sure what else to do - aside from formatting the external drive.
The external drive is 64GB and the Winclone file is 56GB. Could that be the cause of the error? Not sure how much additional space is needed for “incremental” backups.

Can you look in the log? It will give more information on why it is failing.


2021-03-29T18:16:59-04:00:[ERROR] Error writing chunk data to WIM file: No space left on device
2021-03-29T18:16:59-04:00:[WARNING] Truncating “/Volumes/WINCLONE/Windows10Clone.winclone/Windows.wim” to its original size (56636661301 bytes)
2021-03-29T18:17:01-04:00:ERROR: Exiting with error code 72:
Failed to write data to a file.

This was a copy and paste from the Log. I assume the this means there is not enough room on the USB drive.
If that’s the case - and as I said my Winclone file is about 56GB - how large a backup drive should I plan on getting? Would rather not have to keep starting from scratch too often.