Strange issue with certain HD channels
I live in the UK and I'm running Tvheadend on Ubuntu 20.04.2 LTS, streaming using htsp to Kodi clients. The issue I'm having is with a couple of HD channels - BBC2 HD, Channel 4 HD and Channel 5 HD work fine however BBC1 HD and ITV1 HD start ok but after a couple of seconds the video slows dowe and the audio goes out of sync. All other channels work perfectly.
I'm not sure what might be causing the issue so any help would be most appreciated.