The talk page on the wiki has an edit from 2011 from someone else who noticed C3 doesn't have the problem:
This 2014 thread has more detailed info:
Well, it doesn't seem to really crash anything, it's more like the brain gets stuck in a loop. Testing has shown the game isn't stuck in the middle of running any blocking scripts when it happens (which is one reason the creatures can still respond to outside stimuli and break out of it); also, it will ONLY happen in DS or a C3 world with DS docked, which implies it's a bug in the code of the DS game engine itself. You can take the same creature and put it in the same situation on a standalone c3 world and it will NEVER get that problem.
I think it's probably something going on when they are trying to navigate to something and the DS game engine makes some sort of a mistake in telling the creature what the next step is, and they are kind of stuck because that next step is impossible. See, creatures don't have full control during navigation (like when, for example, it decides to 'get food' and there is no food in sight, or they decide to 'eat fruit' but one is not in reach...). What happens is the game scripts call a CAOS command called APPR, which tells the engine to suggest actions to a creature that will get it to approach whatever it's trying to get to... it does this by following smells and sight, and sending messages to its brain that are like strong suggestions by stimulating certain neurons.
The game engine is supposed to keep these suggestions up until the creature gets to the object of it's desire, gives up, or can't get any further (when it gets to a door or elevator blocking its path, a script tells the creature they feel 'trapped' or 'low' or 'high' and then quits, so the creature can use the door or elevator itself, and then, when they are finished and think about whatever they wanted again, they can continue the navigation and keep approaching).
Here, I think what is happening is that during navigation, the game engine makes a suggestion that is not intended due to some kind of bug, and because of this, the creature never completes the original navigation, so the game engine keeps on suggesting that action until the creature makes the navigation end, by deciding on its own that it wants to approach something else (which is not easy with a voice screaming in its head that the door in front of it looks really tasty).
Regardless of how it works though, the result is the same... the game engine keeps stimulating the same neurons, so the creatures get a nonsense suggestion in their brains like a voice repeating the same thing over and over, and if there are no distractions around, they fixate on that suggestion and get stuck in a kind of brain-loop, or trance. The reason I use the word trance here is that a trance state in real life actually IS a brain-loop just like this; a person fixates on one particular thought or frame of mind to the point where they keep sending the same impulses over and over through the same parts of the brain.
These trances only happen to creatures in DS or c3/DS worlds, so, to the creatures' point of view at least, there is some sort of entity in the Capillata that is sending nonsensical telepathic suggestions, and quite literally hypnotizing them. It may be a buggy part of the DS game engine, but it really does manifest in the game as an evil entity which puts creatures into trances with hypnotic suggestion.
For me the easiest way to notice Eat Elevator Syndrome is to do a wolfing run. You will quickly notice norns dying of hunger even though they're surrounded by food, or for other easily-prevented reasons, even during the first generation, because they are spending their entire lives paralyzed in trance. It's actually hard to have a succesful run without supervision as norns keep dying like this, but on a C3 standalone world they're able to survive on their own for generations assuming bacteria and grendels are kept in check.