walk over trigger lines ignored after line-line teleport

[simc]

The player, a voodoo doll or a monster does not always launch walk-over trigger lines placed right after the out going of a line to line teleport.

This occures both in Boom and in UDMF formats and even with ZDoom 1.23 beta 33 but not in Boom 2.02 or ZDoom 1.17c in Dosbox. It appears to start when the actor's speed is higher than 1 map units per tic. Even if the length of the scroll vector line is 33-34 map units. The results are repeatable but there are slight variation between some old major engine versions.

At speed of 4 mu/tic it happens to trigger lines 1-4 mu after the teleport.
At speed of 8 mu/tic 1-7 mu after the teleport. (at least)
At speed of 12 mu/tic 1-11 mu after the teleport. (at least)

The test wad is for Doom2 MAP01. Hit the switch to let the voodoo player teleport a few times. It should cross W1-type trigger lines which lower the bars at the same. Use iddt+iddt and "am_showtriggerlines 2" to see the trigger lines on the automap.

edit: subject title fix (2018-10-12)

[Graf Zahl]

Due to how Doom's line activation works it is generally a bad idea to place any lines close to a teleporter. Behavior will always be erratic and unpredictable and there is no way to robustly fix this, so I won't try.