Heel bone twists strangely under rotation, need to resolve in order to progress I have about 13 animations already made for an armature and now I am getting a very alarming, unexpected result that I need help identifying the cause of and fixing: When I try to rotate the entire model 90 degrees in pose mode, all of the bones rotate together EXCEPT the feet, which rotate in a weird position. Trying to manually correct the feet by rotating the IK bones doesn't rotate the foot bones in the plane of rotation. Instead they twist.





You can see me here trying to turn the foot in a plane parallel to the ground plane (that is, about global z-axis) so that it stays flush with the ground. This is the result:



Here I am showing how misaligned the feet bones are under rotation:



Now, that first foot bone is technically a child of the lower leg, not the IK bones I use to position the feet. But that caused no problems for Sebastian Lague, whose tutorial I followed to rig this guy a couple of months ago:

https://youtu.be/jp_SqjB0468?t=893

My pole targets seem to have no effect on the feet, whereas they do in the video. The feet also rotate in the plane in the video, but not in my project.

Can somebody please help me identify what is causing this problem? I have been fiddling with parenting and constraints for this all day with no success (YES, ALL DAY--like, I woke up working on it, worked on it at Starbucks, and hit nothing but walls until dinner). Every fix I have tried has not resolved the problem, and every other constraint change has ripple effects in existing animations that I will need to correct manually. I am willing to do this.

Here is my file:
It has to do with the Copy Rotation constraint you've given to your feet, if you rotate your IK controller on the Z axis, the foot will go up,  because it's rotating on its Z axis... I don't know if you can fix it with this constraint, but anyway you could simply delete this constraint and parent the feet to the controllers.