wlan2 - sector: lost node, excessive data retries,
why would I get this message?
Normally because the client disappeared, and your MikroTik is stating exactly that - he (excessively) tried to transmit data to it, but did not succeeed. So RouterOS declared this station as “dead” and removed it. You can demonstrate this by pulling the power plug of a client while it is connected to your RouterOS AP.
This is one of the many more detailed log entries MikroTik is starting to give out 