“Is this a common issue with samba” - no.
Samba shuffles rather a lot of data, quite happily. You have not given us an exhaustive description of the shoddy wiring, dodgy switches and wonky configuration that makes up your network. If it was perfect, you would not be posting here.
There is one snag with CIFS (Samba follows MS’s standards and ironically, I think that CIFS is now renamed back to SMB) that I am aware of, so SMB … snag: SMB will indicate that a chunk of data has been received successfully but not that it has been written to disc successfully. NFS will notify that a chunk of data has been written to disc.
The difference is subtle but if there is not a battery backed RAID involved then SMB/CIFS can lose data if the system restarts part way through a write.
Your issue is probably hardware related. Test your network with say iperf3. Have a look at network stats. Don’t rely on cargo cult bollocks - do some investigations. Nowadays we have nearly all the tools as open source to do the entire job - we did not have that 30 years ago. Grab wireshark, nmap, mtr and the rest and get nerdy (or hire me to do it - don’t do that please!)
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.