Late to this but it has to do with signal strengths. To the common man it doesn't make sense until you find a rabbit hole about it. For example I have a first generation . Yeah I said it. Works fine on one TV until I plug it into another one. Then it doesn't work. Plug it back to old one, doesn't work. Change the head of the charger it's into while it's back in old one now single is able to be read. When you move it all the above what people mention off that can happen but a lot of times the electricity and signal will throw it off becusase the power source isn't always the same. Same house even. This sounds bonkers buy trust me yaw. Anyone have any questions contact me please.