I thought that too but i then tried different link partners and they all connect successfully with 1Gbps on the other ports of the router.
It's just port 2 that refuses to report the 1Gbps client capability.
Here is the result when using port3 instead of port2:
[admin@MikroTik] /interface/ethernet> /int eth monitor [find] once
name: ether1_WAN ether2_SWITCH ether3 ether4 ether5 sfp1
status: link-ok no-link link-ok no-link no-link no-link
auto-negotiation: done done done done done failed
rate: 1Gbps 1Gbps
full-duplex: yes yes
tx-flow-control: no no
rx-flow-control: no no
advertising: 10M-half 10M-half 10M-half 10M-half 10M-half
10M-full 10M-full 10M-full 10M-full 10M-full
100M-half 100M-half 100M-half 100M-half 100M-half
100M-full 100M-full 100M-full 100M-full 100M-full
1000M-half 1000M-half 1000M-half 1000M-half 1000M-half
1000M-full 1000M-full 1000M-full 1000M-full 1000M-full
link-partner-advertising: 10M-half 10M-half
10M-full 10M-full
100M-half 100M-half
100M-full 100M-full
1000M-half 1000M-full
1000M-full
sfp-module-present: no
sfp-vendor-name:
sfp-vendor-part-number:
sfp-vendor-revision:
sfp-vendor-serial:
sfp-manufacturing-date:
[admin@MikroTik] /interface/ethernet>