Can't create new backup / delete the old one

[puux]

Has anyone ever had a problem creating a backup / deleting an old one?
I want to migrate data from XR to 13 Pro Max, but quick start is not going and I think I found the cause.
I have some backup from a year ago that I can not delete because it gives an error, I have tried everything on the net and nothing helped.
When I try to create a back up now it gives me a 'creating backup, Estimating Time Remaining' error and so I can wait forever, I have tried the same thing via the PC, deleting the old backup via Mac does not work either.
All the ways on the net do not work, does anyone have an idea how to solve this or knows another way to transfer this data?

 

[now i see it]

If you can’t delete the iPhone backup, try moving it into a different folder. That way Finder (or iTunes) won’t be able to see it when connecting an iPhone.

If the XR is in iOS 14 or later, you should be able to do phone to phone transfer of all data when setting up the 13. No need for a backup.

 

[puux]

If you can’t delete the iPhone backup, try moving it into a different folder. That way Finder (or iTunes) won’t be able to see it when connecting an iPhone.

If the XR is in iOS 14 or later, you should be able to do phone to phone transfer of all data when setting up the 13. No need for a backup.

It is 15.5, I've tried that way, but unfortunately, it stuck on 'Preparing for transfer'... So right now I cannot migrate my data by any means.

 

[puux]

By the way, backuping from iCloud works perfectly on 13, but the copy is one year back so useless.
If only I would create a backup right now it would close the case..