OP-1 not registering drum patches

I’m travelling with my OP-1 at the moment so am using my phone to back everything up over USB-C. I just tried to add a bunch of new drum patches by coping them to a new folder in the drum folder on the OP-1, but when I disconnect the OP-1 there’s no loading screen or anything and the patches have disappeared. When I plug the OP-1 in and check the folder they’ve just been deleted. I know the patches are ok because the same thing happens when I try to copy over patches I’ve previously had on my OP-1. I’ve tried deleting everything except the user presets to make sure I haven’t just run out of space but same thing happens. Copying off the OP-1 to my phone works fine. Has anyone run into a similar issue? I assume it’s something to do with the transfer method and unfortunately I haven’t had the chance to test this on a PC, but it is strange that the files show up in the directory and only appear to be removed when I disconnect the OP-1.