'All channels' recordings don't work

Some of the shows that I have set to record are showing "all channels," which works well when a show switches channels, but sometimes it chooses a channel that I don't get, and worse, CAN'T get. Is there any way to block it from recording those high 300 channels that I can't get. I record because I don't want to miss, and sometimes I don't realize what has happened until its not even available on 'watch now' anymore! I have a whole bunch of worthless recordings, because a bunch of channels got deleted and it picked up unsubscribed channels, even though they're available on subscribed channels.