IC² build 717/718 not working on Cauldron with Forge 1381, works with 1343

I have a Cauldron 1.7.10 private server with IC² installed. I haven't build a lot of different machines yet, I've been busy getting the world set up right, the plugins tuned, the modpack all working together, etc, but everything that I did make worked perfectly up to Forge 10.13.2.1343 and IC² 717. When I upgraded to Forge 10.13.3.1381, all IC2 machines stopped working; they are rendered face-down and their UIs cannot be opened. I updated to IC² build 718 but it made no difference. Meanwhile on my straight Forge-only test server (non-Cauldron), with the same mod versions, everything is fine and all IC² machines work perfectly. I cannot roll back to 10.13.2.1343 without also rolling back CodeChickenCore and a variety of other mods.

Does anyone know of a fix for this problem? I'm guessing it's a problem with cauldron-1.7.10-1.1381.06.221 and all I can do is wait for another new build, but if there's some tweak to make it behave, I'd love to hear it.

(Yes, I know I'm using an orphaned server. But if I want both mods and plugins, I'm kind of short of choices on that front until Sponge actually releases.)

Quote from Chocohead

What plugins do you have, I've seen them cause IC2 machine faces to become screwed up before.

Not a lot of plugins, and I haven't changed them in ages. Dynmap-Towny, DynmapCBBridge, Essentials, EssentialsGroupManager, EssentialsSpawn, LWC, Multiverse-Core, Questioner, TerrainControl, Towny, Vault, WorldEdit, WorldGuard. Of those, the only one recently changed or added was TerrainControl, which is active at world generation time only and I haven't really started messing with it again yet. (And in any case, I re-added it after the IC² problem manifested.) I can't see why any of them would be touching IC², unless it's some kind of fakeplayer issue involving Towny, in which case I would expect it to have been broken all along. (I did have some problems in 1.6.4 getting Buildcraft and TE3 machines that place or break blocks to work inside Towny towns, but it never affected IC².)

No mods were added during the relevant time period, and the exact same Forge mods that are present on the Cauldron server are also present on the Forge test server anyway. (The whole reason for the Forge test server to exist at all is so that I can distinguish between mod conflicts/Forge version issues and mod/Cauldron issues. If it works on the Forge server but not on Cauldron, I know there's some kind of Cauldron-specific conflict.)

I've once previously seen IC² machines render in odd orientations, on a much older server version (1.4.7 I think), but that time they were just rotated and still worked.

Quote from Chocohead

Just as an idea, try removing Multiverse. If that doesn't work, try IC2 on a Cauldron server with nothing else (no mods or plugins) as it might well be broken anyway.

I just got my hands on a Cauldron + Forge 1388 build, and IC2 seems to be working perfectly with this build. So the problem was definitely the cauldron-1.7.10-1.1381.06.221 build.