I doubt that this has anything to do with Cell towers or Cell phones. I think it may have more to do with the latest version of software. I previously thought that this unit had never been updated to the latest version 3.26, but now I'm not so sure about that. I may have updated it when I configured my other controller. It is at 3.26 now for sure since I uploaded the latest software into it after the problem occurred. Castle recommended rolling it back to version 3.2. I don't have that version any longer. So, if I get it from them I'll roll it back and move on.