I found a semi-official report on the QF2/BKK incident. This said that the flaps and gear operated normally for landing.
Perhaps the single flap lever RVDT operates in the same manner as the flap position transmitters. The lever position signal may processed by the Left FCU and a signal is sent to the Flap Input Actuator, but the failure of the other flap lever RVDT's causes the Left FCU to also (attempt to) send a signal to the Flap Bypass Valve. However, the signal doesn't arrive because of Bus #3 failure.
Pure speculation, however.
Rgds.
NSEU