Combination lock not working (GZ version 4.2.4)

[Abba Zabba]

In at least this particular instance, a combo lock isn't functioning properly in GZ.

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In the secret exit house of E1M3 of REKKR, you input a 3 digit code in the proper sequence to unlock a door in the house to progress to the secret exit. However, the door never opens with the correct code. Testing this with Crispy Doom and PrBoom+ had no issues, and the door opened immediately after entering the code in those respective ports.

Rekkr. Requires Doom 1/Ultimate Doom or Freedoom. A simple demo is attached to this post, for GZDoom version 4.2.4.

[Guest]

If the ceiling height of the sector #251 is risen from -198 to -197 the door will open up.

The door opening is done with a dehacked trickery.
However this shouldn't be a compatibility issue. It's not a mapping error. Rebuilding nodes doesn't help either.
There's something odd going on with the item type 693 behavior in GZDoom. It's shooting and aiming.

[simc]

It's a bug in specific conditions. The unopened door in REKKR, the same root cause appears to affect to the playe's own hitscan weapons in GZDoom.

If there are no monsters in sight and with the view centered the player will shoot the pistol to the height of 36 map units. If the player is facing a 36 map units high fence the hitscan pistol bullet will pass that fence but a fence with 37 map units height will stop the hitscan to the sector border. The same way a ceiling at 35 will block hitscan bullets but a ceiling at 36 height will be passed. The same heights seem to apply to Chocolate Doom too.

But in GZDoom If there's a single 2s linedef going across the 36 units high fence sector it will stop and block the hitscan bullets. The 2s line do not require sector changes, line action, tag or special flags. The same type of hitscan blocking happens with 2s lines and ceilings at the height of 36. The blocking doesn't occure if the fence sector floor is lowered by one map unit or if the ceiling block height is risen by one map unit. And this blocking doesn't happen in Chocolate Doom.

Here's a Doom format test map for Doom2 MAP01. Use am_cheat 2 for the automap and to try to shoot the back walls with the player's eyeview centered (mouselook temporarily turned off). You can see the bullet hole decals if you shoot over/under the SHAWN2 textures but not if you shoot over/under the COMPSPAN textures.

A shotgun shot: https://i.imgur.com/Cob7PU7.jpg

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Edit 2019.12.09: Added comment (spoiler alert):

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The dehacked lump sets up an actor called "hitscanDummy".

Thing 79 (hitscanDummy)
Far attack frame = 713
Bits = 2
Initial frame = 241
Mass = 100000
First moving frame = 301
ID # = 693

When it wakes up it starts shooting pistol shots in a remote subsector. One shot every 26 tics. The idea is to lower and raise the sector floor and the dummy so that it can shoot through a low window and hit a gun shot trigger which opens the door.

The dummy can turn to the direction of the player but as it can't see the player it can't shoot up or down. The dummy's shooting height is 16 map units from the ground.

The switches will lower and raise the sector so that it's floor height will be exactly 16 units below the window floor. As there are 2s lines going through the window area the shots will never reach the gun switch at the end.

This seems to have happened since ZDoom 1.17c. The door should open up in ZDoom 1.16.

[Graf Zahl]

I think this shows how few people are playing the game without mouselook. Otherwise this should have shown up during playtesting already.