This is the exact thing I’ve experienced. My skis are pretty noodly though and my BSL is 274. Also skiing at a setting of 6. My theory is similar that with the short boot and the bendy ski it’s flexing out.What's unnerving is that pre-release occurs when I am more or less skiing the fall line and not, for example, at the bottom of a turn.
Double checked the forward pressure and it appears to be in range? I’ll take a photo. Checked the @GregK method last week just for fun, but since it’s a heel release I doubt it’s an AFD setting issue.