I have a Samsung freesat receiver on our narrowboat. I use a dish on the roof which I point at the satellite using a signal strength meter. With it I get a good strong signal and can receive hundreds of channels. When I choose a channel they often play straight away. If I flick through the channels to say filmi-4 it is blank with the error signal "check the signal source" on the TV. If I bring up info it reports there is 100% signal strength. One channel up, say film-4 +1 will play and show the same signal strength. The next channel may not play, again with the same signal strength. If I flick around then sometimes the channel I want will play, sometimes this doesn't work. If I go to the channel guide then sometimes this triggers the channel. If its a HD channel then using the HD option in the channel guide often works. Any ideas? I have looked at all the info on the "missing" channel and can find no difference between it and the ones that play straight away.