van Atten:
Proof Games and more Proof Games

Snap, got beat by 3 minutes. Just about to PM the answer when the "New Comments" notification pops up.

Well, I just solved the Van Atten and when its solution was posted here I just had solved the double-Pronkin one. Haven't even had the time to look at the Heinonen yet.
Ah, my guess was wrong. Still, great problem - wB/wR Pronkins and a tricky hidden cross-capture. And interesting to know it trips up PG engines... do (online) solving tourneys usually have measures against that?
Online tourneys can't have ONLY problems that are untestable, but the directors like to throw in one or two just to stop a blatant cheat from getting a perfect score [plus give the legit solver a chance to surpass the comp].