Recording is no different, it merely saves the digital data from the tuner to the hard disk. Check you haven’t got two versions of channel 4 and drama with duplicates with channel numbers over 800.
You may be watching the good version and recording a dud duplicate. When watching channel 4 live I take it you can live pause, if so that’s the same as recording it.
Welcome to our forum.
See this recent thread
https://myhumax.org/forum/topic/weak-no-signal-9300t