IK rotation locking partially working

Question

So I'm making a fairly rigid robot where only the top most bone on the leg can rotation on Z and the everything below that can only rotate on the X, I read some other posts about not using rotation constraints but instead using the IK rotation lockers on the bone properties instead though it doesn't seem to work perfectly to how I imagine.

You can see here that the top bone which should only twist here is tilting. The other bones seem to work lock rotation perfectly.

Thanks for reading.

Answer 1

Figured it out. It was due to the Pole Target. Removing it resolved the issue.