If your radio is scanning channels and stops, it's because it is receiving a signal. If your programming has a privacy tone PL/DPL on the receive programming, the radio will wait to hear that matched tone before unmuting the speaker. Depending on the radio it may do another round of scanning because of the mismatch on PL/DPL. If you're not on scan, holding on a channel the RX led is there as a courtesy so you know the channel is in use and to wait until the channel is clear before transmitting. For me, I just don't program a receive PL/DPL and leave my receive as CSQ.