CRS312 to UniFi USW-Pro-48 could only link at 1G after a RouterOS upgrade; the RouterBOARD firmware had not been updated

A MikroTik CRS312-4C+8XG (RouterOS 7.13.4) and a Ubiquiti USW-Pro-48 (6.6.61) over 20 m OM3 with SR 850 nm SFP+ optics would only negotiate 1G full duplex; 10G attempts failed with no link and occasional Rx Fault on the UniFi side. Several fibre and transceiver combinations were tested and RouterOS 7.14rc1 did not help.

• Hardware: MikroTik CRS312-4C+8XG, Ubiquiti USW-Pro-48
• Transceivers: 10G SFP+ SR 850 nm
• Form factor: SFP+

Symptoms / messages:

only 1G negotiated
Rx Fault
no link at 10G