RPi4 & TVHeadend jerky playback

I posted about this last year when I last tried to switch over to the RPi4B 4GB. I've just tried again, and until I reached the point of recording using TVHeadend and Hauppauge WinTV-dual HD tuner things were going well. I remembered the suggestion about setting TVHeadend to record in Matroska format but playback is still jerky.

Are there any other settings I can try to obtain playback at the same quality as I get from an RPi3?

I'm assuming that there are people out there who are achieving good results or there would be many posts about it so I'm hoping someone can share the secret.

Just tried an experiment - I copied the files (2 mkv & 2 ts) over to the RPi3 system and they play beautifully so it looks like playback is the problem not recording.

Should have said LE11.0.1

I finally stumbled across the deinterlacing option (I'd been looking on the main settings options and never thought about a context menu), turned it off and a quick test looks OK.