Why does my TV tuner keep dropping out

[shukerr]

Hi,

I've started using my TV tuner for playing audio via the AV1 input.
The car is a S320 - W220 model 2001 with D2B bus for the Comand 2.5 system. Factory fitted TV tuner in boot.

However, the TV tuner has an annoying habit of cutting in and out.
Please see a short video of the fault here:
Mercedes Benz S320 W220 TV Tuner issue on D2B Bus - YouTube

I guess it can be one of three things:
1) Fault on the D2B bus
2) Intermittent power connection to the TV tuner
3) Internal fault on the TV tuner itself.

All of the other D2B devices like CD player and phone work fine so this would suggest the D2B bus is ok.
I've tried to ensure the connections to the TV tuner are ok.

Any ideas?

Thanks in advance.