How do I solve "Error splicing file: Input/output error"?

I am trying to copy a 49.3GB large file onto an external harddisk for backup. I am using Ubuntu 20.04 and after drag and dropping the file I get the error message about splicing failing. Now I checked all answers here: How do I solve "Error splicing files?" and none of them apply. My external harddisk is formatted using exfat

db                                                                                       
└─sdb1      exfat    T7               B4D9-B7F6                             880.7G    53% /media/user/T7

It has enough free space, it is exfat. What else could the problem be? Oddly enough it always fails after 464.4MB, which seems like a very low value. How else can I backup this 49.3GB large file?