I am still seeing issues on 2.13 released firmware when using direct attach SFP28 cables (both 1m long and 3m long purchased from FS.com) when connecting from my CSS610-8G-2S+IN SFP+ ports to Intel XXV710 based 25Gb NICs. I have commented about this in a thread here which also was discussing Intel 500 series NICs where a similar problem was occurring: http://forum.mikrotik.com/t/css610-8g-2s-in-no-link-on-sfp-with-intel-x520/146985/1
The 2.13rc12 firmware works correctly for me with my Intel XXV710 NICs. The 2.13 released firmware does not work correctly. The switch sees the link as being up but the Intel cards see the link as being down.