I frequently see a similar problem, where one of the four chains either doesn’t connect or the indication in the radio is wrong. I don’t know which – the paths usually have some clutter, which could impact one polarization more than the other, but it only happens on one of the two frequencies. This happens on several of our dozens of B5c’s. It’s a mystery.
But your configuration shows an error, the antenna gain set to 0 dB. Thus your EIRP is shown as +24 when it’s really +49, if you have a 25 dB antenna. And you have the RSSI to prove it. I don’t know what country you’re in but I know in the US those frequencies are limited to 30 dBm EIRP, so that’s a total of 5 dBm conducted if using a 25 dB antenna.