It seems that RX unit at MC Room hangs up when LED OFF siganl is transmitted, because when I interrupt the power supply of this unit and reconnect it, the LED gets off at MCH unit, which indicated to me that RX may hang up, and only receives signal from the MCH unit once reset takes place. Because the MCH unit is repeating the LED off signal all the time, the MC Room only captures it on reset.

Is it possible that using DT_INT could be the problem?