Did Leela Zero miss a win in this position?

For what that's worth, Stockfish 11 gives

• Rh2 as +2.6
• Kb4 as +2.2
• Bxc7 as +0.6
• other moves as 0.0

on my machine at depth 45 (will be updating this answer while it digs deeper). Rh2 and Kb4 occasionally switch positions as #1 and #2, so it's still unclear which one of these is truly best. Bxc7 surely isn't, however, at least if you believe Stockfish.

One important note: The top evaluation score has hovered between +2.0 and +2.6 since depth 15. Apparently, Stockfish has not found a way to substantially improve White's position (let alone win) in the last 30 plies. It's still possible that the game will end in a fortress situation with perfect play, and then Leela would in fact not have missed a win (despite having played a suboptimal move).

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Edit:

At depth 54, it's

• Rh2 as +3.9
• Kb4 as +2.2
• Bxc7 as +0.1
• other moves as 0.0

Still not fully conclusive, but we're starting to get somewhere.

In any case, Bxc7 was certainly not the most optimal move that Leela could have played.

Houdini is severely weaker than LC0. I have seen their evaulations of positions, such as in the Salvio Gambit, which Houdini evaluates as only slightly worse for White(clearly not true), where LC0 states that Black has a sizeable advantage.

Thus, it is more likely that Leela had played the best move. We cannot know for sure until we prove a forced win for White in N moves.

Dunno but BxP on c7 looks like a winner to me.

Whether black captures with the rook or not the b pawn marches quickly to become a Q