Observed I was getting a lot of errors copying and packing crates on one USB but not the other, both formatted in exfat - reformatted etc. and still kept getting the errors.
So by chance I pulled up the specs of the one that was working vs the bad one, and saw that the Unit Allocation Size in the working one was set to 1024 where the other was at 128. After formatting to 1024, no more problems.
Just wondering if this may help some experiencing difficulties?