Aim Offsets crumple when adding base pose

Hello,

I’m trying to create an Aim Offset for my character. I’d actually created one that worked just fine until recently (not sure what was changed); although I’ve encountered this issue before.

When I add a base pose to my Aim Offset (or blend it into the anim graph) it contorts and goes very weird.

No base pose:

With Base pose

What game is this? can it be played online or do i need to download it?

Does it work like a games online website? How to operate it?