STX Lite5 ac with the 5GHz interface missing or disabled

Hi there,
Recently bought a pair of STX Lite5 ac (RBSXT5HacD2n) antennas. One of them seems to be OK set up as a PTP bridge server, but the other one (planned to be the client) booted up first time with the 5GHz interface missing. It arrived with 6.34 OS, so I updated it to 6.37.2. No change.
Found a similar problem at http://forum.mikrotik.com/t/solved-new-sxt-ac-testing-wireless-interface-missing/79563/1 so I tried a software reset, a hardware reset and then a 15 sec reset pressing with no netinstall. The interface appeared, but now both the 2 and 5 GHz are disabled by default. Even after manually enabling the 5GHz, it is unable to find any networks around. (The 2Ghz interface works nicely otherwise.)
Even if I enable the interfaces in client or server mode, changing the role disables the interfaces again.
I also tried reinstalling the whole OS using netinstall but it made no change.
The log gives an info: “wlan2: pre-shared key authentication not enabled, disable WPS”, but it means nothing for me.
supout.rif attached.
Thanks for the help in advance.
supout.zip (328 KB)

Send the supout file with an email to support@mikrotik.com explaining your problem.