P_PlayerInSpecialSector: unknown special -258 (Advice requested...)

The player enters the area from the yellow arrow on the right. He/she proceeds to cross one of the series of green lines, all tagged with the action 37 - W1 Floor lower to lowest floor (changes texture). (Indicated by the red arrows.) These lines trigger the sector outlined in yellow, which lowers until it reaches the level of the other NUKAGE sectors that you can see. When it hits that level, it should change from a brown floor to a nukage floor. But it it remaining as the brown floor, and when I step on it, Chocolate Doom crashes with the error in the title.

Any thoughts on why this is happening?

-To my understanding, the flat should alter to whatever is on the front sidedef of the activating line. (ie NUKAGE)
-Even if I only walk over one of the triggering lines, this error still occurs, so I figure it is not caused by multiple triggerings of the line.
-All the nukage sectors have the same floor height, just fyi.
-All the nukage sectors as well as the sector triggered by the action linedefs have Sector effect 7 on them - Damage 2 to 5% health.
-The front sidedefs of the activating linedefs all face onto a single sector, even though that sector has multiple parts.

Any thoughts appreciated. Thanks guys.

Reminds me of this: http://doomwiki.org/wiki/Stairs_create_unknown_sector_types Do you have any building stairs nearby?

No. The only sectors that have moving floors are:
-The three sectors that touch on the sector with the yellow arrow (part of an earlier trap, they lower to the lowest floor once and are done.)
-The main problem sector.

I have run into issues with Action 37 before, though the last time there were several sectors that were affected by this, and moving those sectors and the triggering linedefs around fixed it. This time, there is only one sector involved so I can't juggle things around like that.

KiiiYiiiKiiiA said:

-To my understanding, the flat should alter to whatever is on the front sidedef of the activating line. (ie NUKAGE)

Not sure if this will help you with this particular problem, but just an FYI that action 37 uses a numeric model sector, not a trigger model sector. This means that the sector whose texture and effect it copies isn't the one on the front side of the trigger linedef, but rather the moving sector searches all of its linedefs for the lowest numbered one that has a sector of the correct destination height on either side of it (it doesn't care about which way the linedefs are facing in this case).

Or, to explain it another way, your sector is searching all of the sectors adjacent to it for the ones with the lowest height, and in the case of a tie, it copies the texture and effect from the one with the lowest numbered linedef that touches the moving and destination sectors.

Melon, good sir, you have allowed me to fix the problem.

The linedef with the lowest number adjacent to the triggered sector was on the lower left of the sector, connected to the lower set of stairs on the left. Which would explain why the sector was not changing to nukage when it finished lowering, but was remaining with the brown floor flat. I cut this linedef and moved it to a different section of the sector that was touching on the nukage rather than the brown stairs, and it fixed the problem like a charm.

Thanks Melon and Memfis for the replies.

As an aside, I also managed to sort out a big blockmap problem with this level just today. Man. Problem solving like a boss. :D

Good to see you got it fixed.

If someone is having a problem like this in the future and is wondering if an action uses the numeric or trigger model, you can find out in the tables on this page of doomwiki.org. So in this example, the "Floor linedef types" table has a column headed "Mdl" and the entry for number 37 has "Num" in this column, so it uses the numeric model. Admittedly these tables are for Boom format, but all line actions also present in vanilla work the same way. (And of course, in Boom format you can choose if you want it to have a numeric or trigger model when using generalised actions).