Obtained 41 stack frames.
#0 0x007fbb45681980 in funlockfile
#1 0x007fbb42b1151c in GC_mark_from
#2 0x007fbb42b0c52e in GC_mark_some
#3 0x007fbb42b0c214 in GC_collect_a_little_inner
#4 0x007fbb42b0dcdb in GC_allocobj
#5 0x007fbb42b08091 in GC_generic_malloc_inner
#6 0x007fbb42b0e616 in GC_generic_malloc
#7 0x007fbb42b125ca in GC_malloc_kind_global
#8 0x007fbb42adc815 in mono_gc_register_root
#9 0x007fbb42a866ff in mono_object_new
#10 0x007fbb42a86a07 in mono_object_new_specific
#11 0x00000041e9dfb6 in (wrapper managed-to-native) object:__icall_wrapper_ves_icall_object_new_specific (intptr)
#12 0x0000004221be6e in (wrapper runtime-invoke) object:runtime_invoke_void (object,intptr,intptr,intptr)
#13 0x00000041e9f456 in (wrapper managed-to-native) object:__icall_wrapper_mono_generic_class_init (intptr)
#14 0x00000042492f1b in Pathfinding.Graphs.Navmesh.TileHandler:CutPoly (Pathfinding.Int3[],int[],uint[],Pathfinding.Int3[],Pathfinding.Util.GraphTransform,Pathfinding.IntRect,Pathfinding.Graphs.Navmesh.TileHandler/CutMode,int)
#15 0x000000424801f3 in Pathfinding.Graphs.Navmesh.TileHandler/<>c__DisplayClass42_0:<LoadTile>b__0 (Pathfinding.IWorkItemContext,bool)
#16 0x00000042263338 in Pathfinding.WorkItemProcessor:ProcessWorkItems (bool,bool)
#17 0x0000004226304b in Pathfinding.WorkItemProcessor:ProcessWorkItemsForUpdate (bool)
#18 0x00000042262fd3 in AstarPath:PerformBlockingActions (bool)
#19 0x000000422a129f in AstarPath:Update ()
#20 0x000000421f9e35 in (wrapper runtime-invoke) object:runtime_invoke_void__this__ (object,intptr,intptr,intptr)
#21 0x007fbb428e3458 in mono_get_runtime_build_info
#22 0x007fbb42a8282f in mono_runtime_invoke
#23 0x007fbb42a7eea9 in mono_runtime_class_init
#24 0x007fbb42920993 in mono_set_break_policy
#25 0x007fbb428e3458 in mono_get_runtime_build_info
#26 0x007fbb42a8282f in mono_runtime_invoke
#27 0x007fbb42a82779 in mono_runtime_invoke
#28 0x007fbb46b87c62 in (Unknown)
#29 0x007fbb46b75192 in (Unknown)
#30 0x007fbb46b6695d in (Unknown)
#31 0x007fbb4680bd26 in (Unknown)
#32 0x007fbb4698cd87 in (Unknown)
#33 0x007fbb4698cd41 in (Unknown)
#34 0x007fbb4698d048 in (Unknown)
#35 0x007fbb46bf3c57 in PlayerMain(int, char**)
#36 0x007fbb4529fc87 in __libc_start_main
#37 0x00562a6cc2a029 in (Unknown)
I think it occurs in cases where rectangle navmesh cuts are stacked (only the y coordinate is slightly above).
Crash rates depends on the world. (20% ~ 80%)