I've looked at the best channels and it is already set to the best one, and no it's not just on one device it seems to go out on all devices now and again. it's not placed by any tv or anything.
The SH3, when the devices say that it is connected but there is no internet it has the green flashing wifi light.
and the old router that we had was in a different place to this one now still was doing the same thing.