Broken vertexes on Alembic Skeletal Meshes

I’

m having trouble sometimes with alembic animation datas.
I’m exporting my animated meshes as alembic files in importing them as skeletal meshes in Unreal Engine.
but in some shots , some vertexes moves away for 1 frame. (you can see it on attachment)

for example , an object works fine more that 50 shots but it starts happening in 51th shot and nothing solves it.
I use 3ds max for animation.

why is this happens?

Best Regards