Alembic into UE4 fail?

Hi guys,
I’m trying to import an animation via Alembic into ue4.
I’ve successfully imported an animation that I got from the web (FBX changed into alembic in C4D).
but then I’ve edited a part of it as a separate animation, and it refuses to import!

The settings appear to be the same, but it just fails right out the bat. just writes that it failed.
anyone seen something similar?