You possibly have a broken radio or you are not interpreting what you are hearing or seeing correctly..
I do not have an MD380 but after reading up on the experimental firmware, I note you can only monitor one Timeslot at a time, it is not possible to monitor both Timeslots at the same time..
I have a CS750, this has a switchable monitor function, I select either a TS1 or TS2 channel, hit monitor, all traffic on the selected TS will be heard, the TG and Colour Code and user ID will be displayed..
With the conventional firmware make sure you do not have a 'RX Group List' enabled otherwise you can hear multiple TG's on the selected Channel - but only on the selected channel's TS..
Connect Systems CS750 and CS800, Hytera PD-365, Motorola DP4600
Raspberry Pi 2 and DV4Mini HotSpot
AOR AR-DV1 Digital Voice Receiver / eSPYonARD
WS1088 / TRX-1 / Whistler Q / UBCD3600XLT