was playtesting from editor on level 24, had walked over the quest label a few
times, tux was killed by the 614 that spawns on the label under one of the
barrels, I tried to return to main menu, but the game crashed:

[...]
	SEVERE ERROR
	Tried to assign already assigned quest!
	We will continue execution, quest is:
24_label_test_quest

	SEVERE ERROR
	Tried to assign already assigned quest!
	We will continue execution, quest is:
24_label_test_quest
ASAN:SIGSEGV
=================================================================
==25574== ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc
0x7fdf429d1f02 sp 0x7fff0d47ae50 bp 0x42965be600000000 T0)
AddressSanitizer can not provide additional info.
    #0 0x7fdf429d1f01 (/usr/lib/libasan.so.0.0.0+0x7f01)
    #1 0x7fdf429df4a7 (/usr/lib/libasan.so.0.0.0+0x154a7)
    #2 0x4d1141 (/home/matthias/vcs/git/freedroid/src/freedroidRPG+0x4d1141)
    #3 0x4882e5 (/home/matthias/vcs/git/freedroid/src/freedroidRPG+0x4882e5)
    #4 0x4390a4 (/home/matthias/vcs/git/freedroid/src/freedroidRPG+0x4390a4)
    #5 0x50653c (/home/matthias/vcs/git/freedroid/src/freedroidRPG+0x50653c)
    #6 0x518ff7 (/home/matthias/vcs/git/freedroid/src/freedroidRPG+0x518ff7)
    #7 0x512023 (/home/matthias/vcs/git/freedroid/src/freedroidRPG+0x512023)
    #8 0x5065a4 (/home/matthias/vcs/git/freedroid/src/freedroidRPG+0x5065a4)
    #9 0x417784 (/home/matthias/vcs/git/freedroid/src/freedroidRPG+0x417784)
    #10 0x7fdf41159bc4 (/usr/lib/libc-2.18.so+0x21bc4)
    #11 0x417f2c (/home/matthias/vcs/git/freedroid/src/freedroidRPG+0x417f2c)
==25574== ABORTING


addr2line -e ./src/freedroidRPG 0x4d1141 0x4882e5 0x4390a4 0x50653c 0x518ff7
0x512023 0x5065a4 0x417784 0x417f2c
/home/matthias/vcs/git/freedroid/src/mission.c:208
/home/matthias/vcs/git/freedroid/src/influ.c:1687
/home/matthias/vcs/git/freedroid/src/saveloadgame.c:386
/home/matthias/vcs/git/freedroid/src/lvledit/lvledit.c:252
/home/matthias/vcs/git/freedroid/src/lvledit/lvledit_menu.c:1089
/home/matthias/vcs/git/freedroid/src/lvledit/lvledit_input.c:193
/home/matthias/vcs/git/freedroid/src/lvledit/lvledit.c:281
/home/matthias/vcs/git/freedroid/src/main.c:185
??:?

oops

Tried to reproduce. Could not. Got a bunch of these when the 2 to n times the
quest was added though:

---------------------------------------------------------------------------------
FreedroidRPG 0.15-883-gdb1d4d8 encountered a problem in function:  run_lua 
Error running Lua code: ../map//script_helpers.lua:221: attempt to index global
'FDutils' (a nil value).
Erroneous LuaCode={
2  add_quest("24_label_test_quest", "This is a test quest added by a map label
on level 24.")
3  update_quest("24_label_test_quest", "Now we update the quest.")
4  end_quest("24_label_test_quest", "The test quest has been solved.
Congratulations!")
}

If you encounter this message, please inform the FreedroidRPG developers about it!
You can 

  send an e-mail to                    freedroid-discussion AT lists.sourceforge.net
  mention it on our IRC channel        #freedroid on irc.freenode.net
  or report the bug on our tracker at  http://bugs.freedroid.org/

Thank you!

The problem mentioned above is not fatal, we continue the execution.
---------------------------------------------------------------------------------

ASAN crashes are sometimes hard to reproduce, yes.

The error message you posted happened when walking over the label?

Mmh fogot to ad this when I made the ticket.
Looking at git commits dates, the commit I reproduced this with might be
8c5f5b64bfad8610f6fac7b87bd6dc8f7d8550d0