Thread 1 (Thread 0x7f9816dc9a00 (LWP 12890)):
#0 0x00007f9815ba2839 in __libc_waitpid (pid=pid@entry=12896, stat_loc=stat_loc@entry=0xcacfcc <altstack+7180>, options=options@entry=0) at ../sysdeps/unix/sysv/linux/waitpid.c:40
        resultvar = 12896
        oldtype = 0
#1 0x0000000000538a9e in crash_catcher (signum=11, siginfo=<optimized out>, context=<optimized out>) at /home/crimson/dev/zandronum-sandbox/src/sdl/crashcatcher.c:266
        status = 0
        ucontext = <optimized out>
        dbg_pid = 12896
        fd = {19, 20}
0000002 <signal handler called>
No locals.
0000003 P_TeleportMove (thing=thing@entry=0x3b0f580, x=x@entry=0, y=y@entry=0, z=0, telefrag=telefrag@entry=false) at /home/crimson/dev/zandronum-sandbox/src/p_map.cpp:332
        tmf = {thing = 0x3b0f580, x = 0, y = 0, z = 0, sector = 0x0, floorz = 0, ceilingz = 0, dropoffz = 0, floorpic = {texnum = 0}, floorsector = 0x0, ceilingpic = {texnum = 0}, ceilingsector = 0x0, touchmidtex = false, floatok = false, FromPMove = false, ceilingline = 0x0, stepthing = 0x0, DoRipping = false, LastRipped = 0x0, PushTime = 0}
        oldsec = <optimized out>
        box = <error reading variable box (Cannot access memory at address 0x7fff72430fe0)>
        ld = <optimized out>
        it2 = {minx = 0, maxx = 0, miny = 0, maxy = 0, curx = 0, cury = 0, block = 0x0, Buckets = {0 <repeats 32 times>}, FixedHash = {{Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}}, NumFixedHash = 0, DynHash = {Array = 0x0, Most = 0, Count = 0}}
        th = <optimized out>
        StompAlwaysFrags = <optimized out>
        it = {minx = 0, maxx = 0, miny = 0, maxy = 0, curx = 0, cury = 0, polyLink = 0x0, polyIndex = 0, list = 0x0}
0000004 0x0000000000693d05 in P_Teleport (thing=thing@entry=0x3b0f580, x=0, y=0, z=<optimized out>, angle=2147483648, useFog=useFog@entry=true, sourceFog=true, keepOrientation=false, bHaltVelocity=true) at /home/crimson/dev/zandronum-sandbox/src/p_teleport.cpp:161
        oldx = -6291456
        aboveFloor = <optimized out>
        player = 0x168b440 <players>
        an = <optimized out>
        oldy = 0
        destsect = <optimized out>
        oldz = 0
0000005 0x0000000000694248 in EV_Teleport (tid=<optimized out>, tag=<optimized out>, line=<optimized out>, side=<optimized out>, thing=0x3b0f580, fog=fog@entry=true, sourceFog=true, keepOrientation=false, haltVelocity=true) at /home/crimson/dev/zandronum-sandbox/src/p_teleport.cpp:393
        angle = 0
        vely = 0
        OldAngle = 2147483648
        z = <optimized out>
        velx = 0
        haltVelocity = true
        keepOrientation = false
        sourceFog = true
        line = <optimized out>
        tid = <optimized out>
        side = <optimized out>
        fog = true
        thing = 0x3b0f580
        tag = <optimized out>
0000006 0x00000000006505b0 in LS_Teleport (ln=<optimized out>, it=<optimized out>, backSide=<optimized out>, arg0=<optimized out>, arg1=<optimized out>, arg2=<optimized out>, arg3=0, arg4=0) at /home/crimson/dev/zandronum-sandbox/src/p_lnspec.cpp:851
No locals.
0000007 0x000000000078cc7c in ASectorAction::CheckTrigger (this=0x3b11460, triggerer=0x3b0f580) at /home/crimson/dev/zandronum-sandbox/src/g_shared/a_sectoraction.cpp:122
        res = <optimized out>
        triggerer = 0x3b0f580
        this = 0x3b11460
0000008 0x000000000078cd8e in ASecActHitFloor::TriggerAction (this=0x3b11460, triggerer=0x3b0f580, activationType=5) at /home/crimson/dev/zandronum-sandbox/src/g_shared/a_sectoraction.cpp:181
        didit = <optimized out>
0000009 0x0000000000666032 in AActor::CheckSectorTransition (this=0x7fff72431030, this@entry=0x3b0f580, oldsec=0x1, oldsec@entry=0x3b04330) at /home/crimson/dev/zandronum-sandbox/src/p_mobj.cpp:4424
        act = 0
0000010 0x0000000000656517 in P_TeleportMove (thing=thing@entry=0x3b0f580, x=x@entry=-6291456, y=y@entry=0, z=0, telefrag=telefrag@entry=false) at /home/crimson/dev/zandronum-sandbox/src/p_map.cpp:435
        tmf = {thing = 0x3b0f580, x = -6291456, y = 0, z = 0, sector = 0x0, floorz = 0, ceilingz = 8388608, dropoffz = 0, floorpic = {texnum = 2514}, floorsector = 0x3b03e70, ceilingpic = {texnum = 2594}, ceilingsector = 0x3b03e70, touchmidtex = false, floatok = false, FromPMove = false, ceilingline = 0x0, stepthing = 0x0, DoRipping = false, LastRipped = 0x0, PushTime = 0}
        oldsec = 0x3b04330
        box = {m_Box = {1048576, -1048576, -7340032, -5242880}}
        ld = <optimized out>
        it2 = {minx = 0, maxx = 0, miny = 0, maxy = 0, curx = 0, cury = 1, block = 0x0, Buckets = {-1 <repeats 16 times>, 0, -1 <repeats 15 times>}, FixedHash = {{Actor = 0x3b0f580, Next = -1}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}, {Actor = 0x0, Next = 0}}, NumFixedHash = 1, DynHash = {Array = 0x3b8cf00, Most = 0, Count = 0}}
        th = 0x0
        StompAlwaysFrags = true
        it = {minx = 0, maxx = 0, miny = 0, maxy = 0, curx = 0, cury = 1, polyLink = 0x0, polyIndex = 0, list = 0x3ade118}
0000011 0x0000000000693d05 in P_Teleport (thing=thing@entry=0x3b0f580, x=-6291456, y=0, z=<optimized out>, angle=2147483648, useFog=useFog@entry=true, sourceFog=true, keepOrientation=false, bHaltVelocity=true) at /home/crimson/dev/zandronum-sandbox/src/p_teleport.cpp:161
        oldx = 0
        aboveFloor = <optimized out>
        player = 0x168b440 <players>
        an = <optimized out>
        oldy = 0
        destsect = <optimized out>
        oldz = 0
0000012 0x0000000000694248 in EV_Teleport (tid=<optimized out>, tag=<optimized out>, line=<optimized out>, side=<optimized out>, thing=0x3b0f580, fog=fog@entry=true, sourceFog=true, keepOrientation=false, haltVelocity=true) at /home/crimson/dev/zandronum-sandbox/src/p_teleport.cpp:393
        angle = 0
        vely = 0
        OldAngle = 2147483648
        z = <optimized out>
        velx = 0
        haltVelocity = true
        keepOrientation = false
        sourceFog = true
        line = <optimized out>
        tid = <optimized out>
        side = <optimized out>
        fog = true
        thing = 0x3b0f580
        tag = <optimized out>
[...]

changeset: 4127:b5139bc0df8d
[...]
description:
out of sequence fix backport from ZDoom revision 3455:
- Fixed: Teleports that were not initiated by walking would not trigger sector actions.

Quote from Graf Zahl
I think the rules for 'actor hits floor' are stupid and too general, this really shouldn't trigger if a sector is entered by teleporting. This was just one of those stupid things that got reported as a bug and Randi dilligently changed it without thinking about the consequences. In any case, recursive teleports, like what happens in this setup are a surefire way to crash the engine, there's not much that can be done about it other than delaying the teleport with a script.