I have a receptionist with 2 PKM 24 units. The second one will go offline and the only way I can get it back online is to remove the attached device and then readd it. Seems to be totally random. It'll go months with no problem and then happen twice in the same day. The first PKM never goes offline, only the 2nd one. Tried swapping them, setting up on another phone, changing the connecting cable, same issue. Any ideas?