I just solved a very annoying problem. I have lots of OS sensors around the house and I started losing contact with almost all of them, all at once. It was intermittent and would come and go every few hours or so.
Finally tracked it down to a version 2.1 ultra-cold sensor with weak batteries. It was continuously transmitting an un-modulated carrier, and blocking all of the other sensor signals. The little red transmit LED in the sensor was continuously illuminated; that was the only indication that something was amiss. A change of batteries solved the problem.
I only found it because I had an ICOM handheld radio that I could tune to 433.92MHz. I walked around looking for where the signal was strongest. I don't know what I would have done w/o the radio...maybe just replace the batteries in every sensor.
I don't know if the version 3.0 sensors will do this with low batteries. But, if you suddenly lose contact with all your sensors, this would be one possibility to consider.