DP48 Talkback Function(FW1.9) not working with daisy chained units


I have been trying to get the talkback function on the DP48s to work but found that once they are daisy chained together these units will not be able to go into the talkback mode.

I was wondering why 1 of the units was able to show TALK when I press and hold the MIC button but not the others. After much trial and errors I realised that when the units are daisy chained, they will not go into the TALK mode.

I managed to cause 1 DP48 to hang when I turned on a downstream unit before turning on the source DP48, the unit goes into TALK mode after I press and held Mic button but it got stuck and doesn't return to main screen after I let go of the button. I had to restart the unit.

Seems like a bug in the firmware? Or is it a requirement for the DP48s to be directly connected to HUB4 without any units connected to its thru port but this is not documented.