So I got a couple of the 2013 Mac Pros each with a SANLink2 10G SFP+ connected, one running macOS 10.14.6 and the other macOS 10.15.3. I started having an issue with large SMB downloads hanging in the Finder and in apps. You'd start the file copy and it be copying along nice and fast and then the data being received over the network would go form 400 MB/sec to like 230 KB/sec and just hang. If you tried to stop the copy in the Finder it would take like 3 or 4 minutes to eventully stop.
Had to turn off RSC and TCPipv4Checksum via the SANLink Utility and reboot to fix the issue. Is anyone else having this issue?