Having the same issue with MS-01 and X710 on latest Proxmox and passthrough.
I have to disable/enable the interface on the switch or unplug and plug back the DAC.
Tried two DACs and two SPF+ RJ45 modules. No difference,
Using CRS312-4C+8XG as switch and Mikrotik XS+DA0001 DAC. Mikrotik S+RJ10 also not working.
Contacted Mikrotik support and they advised to upgrade to a 7.15.something beta. Same issue.
So, 7.14.2, still same issue.