Confirmed RVZ1 Lowering Lava Section does not damage Player.

[frozenLake]

https://gfycat.com/GeneralBriefBarbet

As you can see, sonic does take damage from the lava up until the button is pressed, which then the lava in that area becomes harmless.

 

[RazeZX]

Interesting...
Well, i'm not a developer so i can't be sure of anything but, this also happened to my map
I CURRENTLY DON'T HAVE A GIF, BECAUSE AT THIS MOMMENT MY ROUTER IS BROKEN
Isn't same case, but is happening.
I'm not pretty sure but, i don't know if there's an way to keep lava physics with much other effects (and i also don't think someone would suicide itself in lava)

 

[glaber]

This bug has reared it's head again. and I have found more information on this bug.
Apparently this is tied to the action 404-Move Tagged sector's ceiling. This means that it's only the top of the lava fof that's affected.

I attached a lava test wad to show the bug

 

[toaster]

This is an order-of-operations bug. The damage check is after the lava has moved but before the player has fallen down onto it. You can enable this improved behaviour with #define SECTORSPECIALAFTERTHINK in doomdef.h, which is commented out in 2.1 builds but flipped on in one of my extant branches in internal.

One of the interesting side effects of this fix is that the player no longer uncurls from jumping or rolling frames for one pic when hitting a death pit.