Applying RP IK causes rotations

[Anonymous]

This is a weird glitch. Simply applying RP IK to a joint chain causes the joints in the chain to rotate slightly.

I have several students reporting this problem.

I have not been able to reproduce the problem with any combination of joint chains I've drawn, but I have attached a scene file with a 3 joint chain from a student file where the joints will rotate when RP IK is applied.

The workaround has been to draw a new joint chain by snapping to the old joints and matching the orientations. Applying RP IK to the newly draw joints does not cause rotations.

I have no idea why this is happening, which is an unsatisfactory answer to give to students. I would love to have a proper answer.

Using Maya 2019 Educational Licenses.