In a few cases it may happen that, due to large sources of radiation, noise in the frequency or even inhibitors of security vehicles interfere with the signal of Ajax wireless devices.
Also, the infrastructure of the facility and the materials of the place can generate such circumstances.
The test we recommend doing is to change the position of the sensor, with that of another one that is working properly. This will make it easier to determine if the cause is related to an external factor or the sensor itself.
Read also this related FAQ (present in all languages).