With the use of SFP module with fiber for each direction it can easily happen that one direction lose the link connection. When this happens on Tx side, interface does not detect as link is down. Such case create Unidirectional link as Rx works, but Tx not. Unidirectional links (UDL) pose the issue for networks as they can cause STP algorithms to make incorrect decisions to block or allow alternative paths.
To mitigate UDL issue, Mikrotik can implement DLDP as specified: https://www.h3c.com/en/d_201808/1102747_294549_0.htm
Many switch vendors like TpLink, HP, etc. already support DLDP.