Glitch on Two Knights vs Pawn Practice

Every time I open the exercise and make the first move, 1.Ng6 I get a positive evaluation and it goes from a mate in 15 to mate in 12.
Starting position -
After 1.Ng6 -

But if I make a mistake and try from the beginning 1.Ng6 I get a negative evaluation.

1.Ng6 after retry -

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