There are a couple of animated signs around Bricks (Casinox area and Tenements), animation on which got disabled while patching the game. It is not really clear why it was done, it seems that at some point they were crashing the game. The game doesn't seem to crash anymore or at least that never really happened during testing so they are somewhat back.
How they were fixed
The solution is more of a workaround. As I understood from the documentation all models which have animation state amb_a would play it on spawn as their idle animation.
The game has a way of marking entities with tags to determine what class of objects the said entity belongs to. This can be done at /anoxdata/models/entity.dat.
The signs were marked as noclip. Many other objects have a general tag, marking the signs with that didn't do much. So in the end I just marked the signs as flying characters and it worked. The animation is now playing and the signs are kept in place, they are not clickable anyway so I suppose it doesn't really matter if they are marked as character or not. Marking them as normal characters and not flying would make them affected by gravity which displaces them.
I'm a little bit foggy (being this was well over a decade ago now), but what I'm able to recall from talking to Joey about why the animated signs were disabled is that they caused a memory leak.
Not entirely sure how this occurred - could still be confirmed if this is the case with an analysis tool - but it is quite neat to see them working.
It's hard to tell why would the signs make any difference regarding memory/stability. At this point they are treated as characters with an idle animation that don't do much else. The only thing I can think of is that maybe there are too many frames used in idle animation or that at some point there was a separate mechanism to handle them but now it's not present.
That's good to know, need to test them more to know for sure.