I had this issue persisting the other day. I couldn't figure out why it was happening, until I checked the base stations. Someone had put greasy finger prints all over the face of one of the base stations. I'm pretty sure the finger prints were causing reflecting issues from the lights in the room, or maybe just obstructing the signals.
I cleaned the face of the base station, made sure it was pointing in the correct direction and it worked. The only thing I changed was the cleaning of the base station face.
Hope this helps someone.
