Feed icon from IOP feed only shows correctly when the feed is empty

[heafnerj]

The icon for the IOP European Journal of Physics and other feeds from that domain only displays correctly when the feed had no new items. If there are new, unread items the icon reverts to a generic plain icon. The EJP feed is http://iopscience.iop.org/journal/rss/0143-0807. The problem is this only happens on my iPhone running iOS 17. It doesn't happen on my iPad Pro (running iPadOS 17) or my Macs (running Sonoma). This has been a problem for years and I have no idea how to fix it. I've tried deleting the feed and adding it again. Nothing seems to work.