CLK heating blows cold on corners

It could be a problem with the dampers or their servos in the ducts. Try the ACC test/reset:

With the engine running, simultaneously press and hold the RECIRC and FRONT DEFOG buttons until their indicator lights begin to blink. They should blink 20-30 seconds then stop. If they don't stop, then you have a damper control problem and will nee proper equipment (SDS) to diagnose.

It's possible there is a short in a servo that only occurs with the G-forces in corners. It could also be a defective duo valve where the coolant is routed into the heater core. For a bad part, it might not take much G-force to trigger it.