At 50 RA' the automatic flare is initiated. Could this have contributed to a stall ?
If the DFCS was only in CMD B, which is what has been stated so far, then FCC B would have not gone into the flare mode since the right radio altimeter was outputting the correct RA. FCC B would have been the master FCC and it uses the right radio altimeter unless a failure flag from the right radio altimeter transceiver is present (it then would switch to the left).