rsync was written by one of the original Samba developers. I wonder if Tridge and co have any idea about how to shuffle data from A to B safely?
CIFS/SMB will only indicate received and not received and written. This is unlikely to be an issue.
I would start by proving that my network works properly, especially that dodgy cable with only wires 1,2,3,7 connected - because that’s all 100Mb/s needs, or the solid core cable that runs for 150m with plugs at each end instead of sockets and drop leads.
Have you been distracted and typed a password/PSK in the wrong field 8)