Left Arm IK and Right Arm IK not working the same?

So I am setting up an IK system to strap a GLTF rider model to a horse.
The model in rest looks like this:

There are two transform nodes/bone anchors on the equine that serve as the targets for each IK system and the pole targets are dynamically generated.

The pole targets are in the correct spot, but only works for the left arm. I’ve tried messing with the poleAngle on the right arm to no avail.

Basically no matter how I set this up the right arm is always “inverted”?

The left pole target transform position

The left target

The right pole target transform position

The right target

What should I be modifying to make both arms behave the same way?

Actually I think I figured out why.
Looks like the underlying bone alignment is not the same.

Would there be a quick way to fix this without re exporting the mesh?

I do not know as I am stupid with IK but maybe @MackeyK24 or @adam might know ?

Answerring from the couch, I seem to remember having similar issues before. Think PI is going to be involved, but will check. Do not remember if making poses matching the other side are reversed with the setup (pole angle) or targets (maybe both).

I am almost manufacturing my skeletons in Blender, so things are standardized. Just using some random skeleton for IK seems “challenging”.

Yeah I bounced the model back to the rigger and was like bro align those bones to have the same forward and up axes and a mirrored right axis.

It’s probably impossible to fix otherwise.