I went to software decoding (which admittedly did fix problems when playing back on our main TV through the Shield TV 2019 - a device that can play basicaly ANY file, so goodness knows why Channels doesn't work with hardware decoding on that), anyway, it seemed to fix the blacking out of the picture but still the audio going slowly out of sync remains.
I mean, its a 2022 model Sony Android (now Google) TV and it plays any recorded TS files from OTA Freeview on Kodi so I cannot put the blame on the TV not supporting audio when it clearly does.
I'm afraid there are just too many problems with the Android app and Channels itself to justify laying out the cost for another year, so I'm out.
I have the Channels server on my Synology DS1821+ with HDHomerun doing the OTA duties. As the DS is an AMD unit there is no hardware transcoding and anyway, as I've said, Plex manages to play live TV and recordings without going OOS and the HDHomerun app can also do it better than Channels.
I'm going to have a try with TVHeadend and Jellyfin or suchlike, maybe stick with Kodi for recording with TVHeadend and just play the recordings back through Plex as the DVR offering on Plex is equally excruciating to use, just in a different way to Channels.
I thought Channels would be the answer, but it's not, certainly not for Android TV which seems like an afterthought and certainly not for UK viewers.