unity crash when program exits normally

sometimes when I exit game normally in ios, crash can be issued. the following is callstack:

libsystem_kernel.dylib 0x00000001989171e0 __pthread_kill + 8
libsystem_c.dylib 0x000000019888ab78 abort + 132
libsystem_malloc.dylib
0x0000000100bffa58 Renderer::ClearPropertyBlock() (Renderer.cpp:294)
0x0000000100dc79f0 Animator::ClearRelatedPropertyBlocks() (Animator.cpp:1053)
0x0000000100dc79a8 Animator:eactivate(Unity:eactivateOperation) (Animator.cpp:149)...

unity crash when program exits normally