Two issues, first my son as it's more pressing.
Some of you may remember my initial post with a video had him falling leaf all the way down. Now that I've started riding and I actually prefer toe he's stopped with the falling leaf and is doing toe. Problem is major ruddering toe side. He's really good heel, toe has some major throwing his hip and board around. Is this typically a not enough toe pressure and not using enough shoulder direction to get you going where you want to go? Spring corn probably isn't helping as I think he really has to keep his board on top of it.
Tough I guess without video, but at this point I'll crash and die a horrible death if I try to follow him and video. I can't quite disconnect my brain from body movements yet, though getting better.
As for me, I'm the opposite. I love my toe turns and am getting pretty good edge and beginnings of carves. My heel side though I always seem to over rotate and end up in a side slide. I initiate ok, don't think I'm ruddering, but I seem to turn just a bit too much and wash out the tail. I'm thinking perhaps weight not forward enough and not driving through the turns?
I bet you are both being static in the waist, knees and ankles which is causing this problem. It will improve with practice, but I would recommend a lesson to adjust and prevent bad habits from forming.