Not well done MikroTik - hardware related problem?
And why when you switch to SwOS there is no such problem, only CRS3017 with RouterOS?
Same hardware - different behavior = simply software bug!
I can confirm that CSS326 working fine with 2.9 and there is still RX overruns.Upgraded two CSS326 from 2.7 and it worked fine. Still having RX overruns.