The only thing I can think of that you might not have taken into consideration...any FAT32 formatted drives you have only support file sizes up to 4GB. If your temporary folder that WBFS Manager is using is FAT32 I suppose you could have this problem.
I'm gonna buy another Series X, but can't decide if I should wait till the Xbox June event (maybe they get discounted) or just buy now. What do you guys think?