Thanks for the quick response!
My username is kazerniel.
So when I go to the feed linked in the OP (set to show newest first) and try to filter the first story via the “events” tag:
I click save training, it says “saving…” and the modal disappears, but the story doesn’t disappear despite feed being set to hide hidden stories. I open up the menu again, and the “events” tag appears unselected again:
On the other hand when I tried to filter another post via the “ice” tag, that worked (I set the feed to show hidden stories to illustrate) :
