When setting an image defined in ANIMDEFS to warp to render on the HUD, the images no longer warp correctly. This behavior worked until the latest version and works on the newest version of ZDoom, so I'm assuming it's a bug.
I discovered this through the following code. The basic premise is that when the player is under liquid, a texture is rendered on the HUD. That texture is made to warp using an ANIMDEFS lump. Here's the relevant code: