Ok, I have TVHeadend 4.2.8 running on a Synology NAS, yes I have a fully working and populated EPG (UK freeview). TVHClient on the ATV displays a full epg without any issues, in comparison.
This is how the guide looks
!rsz_img_20191125_175107.jpg!
This shows some of the missing images for recordings (I could actually select them, I just missed the highlighted text underneath)
!rsz_img_20191125_175224.jpg!