6m is quite a big distance, I usually aim to have it much nearer than that. And though I do lose signal, particularly when I leave the room and forget to take my phone, when I go back in range it soon reconnects and replaces the missing data.
Having said that, I do occasionally get problems near the end of a sensor or the end of a transmitter. (And I had one transmitter fail early and before it failed I kept losing signal);
Remember that the transmitter only sends a signal every 5 miniutes, so if you go out of range and back in again it can take 5 minutes to reconnect. (And I've tried turning bluetooth on and off on my phone but don't think that speeds things up.)
Dexcom support are very helpful if you have any issues with your sensor or transmitter so I suggest you also consider phoning them for advice.