Couldn't place lregion type 0!

[elunna]

Not recorded with rr, so not much to go on.

Suddenly, the dungeon collapses.
Couldn't place lregion type 0!
Generating more information you may report:
#0  __pthread_kill_implementation (no_tid=0, signo=6, threadid=140737339652032)
    at ./nptl/pthread_kill.c:44
#1  __pthread_kill_internal (signo=6, threadid=140737339652032)
    at ./nptl/pthread_kill.c:78
#2  __GI___pthread_kill (threadid=140737339652032, signo=signo@entry=6)
    at ./nptl/pthread_kill.c:89
#3  0x00007ffff737d476 in __GI_raise (sig=sig@entry=6)
    at ../sysdeps/posix/raise.c:26
#4  0x00007ffff73637f3 in __GI_abort () at ./stdlib/abort.c:79
#5  0x0000555555a98616 in NH_abort () at end.c:235
#6  0x0000555555a9f85f in panic (str=0x5555566454e0 "%s") at end.c:800
#7  0x000055555602892e in impossible (
    s=0x5555565ee9a0 "Couldn't place lregion type %d!") at pline.c:685
#8  0x0000555555db51fd in place_lregion (lx=61 '=', ly=3 '\003', hx=75 'K', 
    hy=19 '\023', nlx=21 '\025', nly=1 '\001', nhx=57 '9', nhy=16 '\020', 
    rtype=0 '\000', lev=0x7fffffffdd30) at mkmaze.c:319
#9  0x0000555555db6bd6 in fixup_special () at mkmaze.c:501
#10 0x0000555555dbb685 in makemaz (s=0x603000000a9a "minetn") at mkmaze.c:1028
#11 0x0000555555da438e in makelevel () at mklev.c:929
#12 0x0000555555da7adc in mklev () at mklev.c:1389
#13 0x000055555587292b in wiz_makemap () at cmd.c:928
#14 0x00005555558a73fa in rhack (cmd=0x55555690ba00 <in_line> "v") at cmd.c:5812
#15 0x00005555557974bb in moveloop (resuming=0 '\000') at allmain.c:812
#16 0x00005555564c2dce in main (argc=0, argv=0x7fffffffe4a8)
    at ../sys/unix/unixmain.c:353


Program received signal SIGABRT, Aborted.
__pthread_kill_implementation (no_tid=0, signo=6, threadid=140737339652032) at ./nptl/pthread_kill.c:44
44	./nptl/pthread_kill.c: No such file or directory.
(gdb) p moves
$1 = 11660990
(gdb) p u.uz
$2 = {dnum = 2 '\002', dlevel = 3 '\003'}
(gdb) p u.umonster
$3 = 762
(gdb) p u.umonnum
$4 = 762
(gdb) p urace.malenum
$5 = 339
(gdb)