If the sensitivity on one of the baby units is very high, for example H, then this baby unit will indeed continue to transmit continuously and the parent unit cannot switch to the other baby unit. Set both baby units to D or E, and the scan function on the parent unit will work better. Bear in mind that this function requires a lot of power from the parents' unit, so charge the parents' unit daily with the parents' unit switched off and use the parents' unit during the scan function with the power adapter connected as much as possible.