Comentário oficial
Can you tell me which model of Kingston drive it is? Just because a drive is of USB 3.1 standard, doesn't mean it necessarily has fast read/write speeds for masses of small files - this is typically where many drives fail to shine, and this small file management is what's happening when the collection is being updated on your export drive.
Also, let me know what format the drive is - FAT32 or MacOS (HFS+)?
My first recommendation would be to try reformatting the drives and export all the contents anew. See if subsequent exports / edits suffer the same problem.