If I get "out of plane" what I end up doing is approach the bucket carefully, and check to see which arm is "forward" more than the other. Then initiate contact with the forward arm.
Then either inch forward a bit more to force the forward arm back, (and simultaneously extend the laggard) or give the curl function a very slight motion, to extend the arm that is behind.
If the forks are sitting on snow, the curl bump works better, because pushing on the forward arm against the bucket with the HST wants to just slide the attachment away from me.
JWR, I'm sure mine works this way. I'll go out and get a few pics of the pivot points. I'll need a ladder, because the front blower is on and I don't remove the loader. I just remove the bucket, raise it up high enough to walk under yet allow the tractor to fit under the upper header on the garage door, then I hydraulic lock the arms in that raised position. The curl hoses are unhooked (they rotate my chute on the blower) so I won't be able to demonstrate any movement.