Per Occam's Razor, I guess that makes more sense. In that case, I guess what I'm seeing is good old fashioned
nasal demons Undefined Behaviour.

It still doesn't make much sense that Lava is able to cause such a thing though.

Actually, it might be related to the way Skops makes the screen scroll, and the lava moves with it. That at least is likely what that enumeration over them in the Skops code is for. Maybe the Lava events themselves are trying to mess with the screen and it doesn't work correctly in EDU. It might be best to make them TYPE_EAU instead to avoid this nonsense, although I'm not sure that that works properly in EDU either (water is suspiciously absent from the Rising Tides level).
On a somewhat unrelated note, the idea of Skops being able to reverse the directions too made me think that he himself might have been the Big Bad early in development. On further reflection that does seem unlikely, but it got me thinking about the fact that the final world was at one stage going to be an Electrical world, before they replaced it with the Cake theme. That may be where the concept of the UFOs came from originally (or at least their wiring and indicators), and might even explain why
this was present in Cake. Might be best for me to take this particular discussion to the main Rayman 1 topic.
Speaking of UFOs, I can now confirm that the code still works in Designer, but it expects the event to start in Etat 0 and SubEtat 0, and then moves it into SubEtat 1 when Rayman jumps on it, just like in EDU, and unlike in Rayman 1 (where the SubEtats are 13 and 14). If the event doesn't start in SubEtat 0, then it doesn't work at all. So unfortunately you can't just turn a cloud or pencil sharpener into a UFO. This really feels like one of those things that didn't need to be hard-coded!
Now I understand this hard-coding, I'm starting to get why they reorganized the UFO-related ETAs in EDU. In Rayman 1, the UFO states were on the end of (what was presumably even then called) IDC.ETA, and the lever states were (for some reason) buried in the middle of PNG.ETA, in allfix, and the respective event behaviours were hard-coded to use the particular Etat/SubEtat values therein. This was no longer sufficient in EDU, where they needed completely different sprites for the UFO and lever in Image, while still allowing them to work in Cave. So they broke the lever out into its own ETA/DES pair, presumably called LEV.ETA/LEV.DES, with just two states available, only in Cave. They then created LEV2.ETA/LEV2.DES in Image, with the same states, so the same event code could use both. Ironically, they didn't even use the Cave levers in the final game, but everything's still there to make them work.
Breaking out the UFO itself is a bit less justifiable, since the relevant ETA and DES weren't in AllFix, but obviously they wanted to be able to duplicate IDC.ETA/IDC.DES exactly between Cave and Image. So again, they broke out the UFO into a small ETA/DES pair in Cave, with only two states available, and then created an Image equivalent with a Palette sprite, and no engine sound.
The biggest mystery here is why in Rayman Designer, they cut the ETA/DES containing the Palette, while keeping IDC and LEV2. It makes no sense from a space standpoint, since the palette is literally just a single sprite, while the other two contain several animations.
EDIT: I used the code you posted a few pages ago to port over the Palette to Designer. It feels a bit like cheating, but it works perfectly.
