At first, I did not know why/how this error ocurred, investigating deeply and after many hours I realized that my server crashes when a monster uses waterball skill such High Wizard MvP, Turtle General, Drake, Strouf, etc.
Here is the error in GDB.
Program received signal SIGBUS, Bus error.
skill_delunit (unit=0x7fffeccf7044) at skill.cpp:18410
18410 switch (group->skill_id) {
(gdb) bt full
#0 skill_delunit (unit=0x7fffeccf7044) at skill.cpp:18410
group = 0xfdfdfdfdfdfdfdfd
#1 skill_delunit (unit=0x7fffeccf7044) at skill.cpp:18389
No locals.
#2 0x000055555575199d in skill_timerskill (tid=<optimized out>, tick=134544835, id=<optimized out>, data=<optimized out>) at skill.cpp:4206
src = <optimized out>
target = 0x555559a09cd0
ud = 0x7fffe49e0a1c
skl = 0x7fffe4a3c28c
unit = <optimized out>
range = <optimized out>
FUNCTION = "skill_timerskill"
#3 0x000055555557aeae in do_timer (tick=<optimized out>) at timer.cpp:374
tid = 628
diff = -1
#4 main (argc=<optimized out>, argv=<optimized out>) at core.cpp:368
next = <optimized out>
thanks in advance