Berserk 13 or polyglot or xboard problem?

[chesskobra]

I got this error a few times while running a Stockfish 16.1 - Berserk 13 match in xboard:

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{polyglot: resign (illegal engine move by white: c4d5)}

In all these games Berserk lost from a good position on the board due to the error. Anybody knows what is happening?

[hgm]

Almost certainly a Berserk problem. To make sure you would have to look at the position where this error occurred, to make sure the refused move was indeed illegal.

[chesskobra]

They are in fact illegal moves. Here are the positions and moves if the author of Berserk is here and would like to take a look. This happened in 7 out of 14 games, so I abandoned the match.

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{2n5/8/P7/2k5/1R5P/4P1K1/8/8 w - - 3 56} {polyglot: resign (illegal engine move by white: e6d5)}
{k2r4/pn3r1p/2BP2p1/3P4/P7/4RPB1/6KP/8 b - - 2 46} {polyglot: resign (illegal engine move by black: e7e5)}
{rn1qkb1r/pp2pppp/5n2/3p4/2PP2b1/5N2/PP3PPP/RNBQKB1R w Kq - 1 6} {polyglot: resign (illegal engine move by white: d4c5)}
{r5kr/1p3pp1/p1n2nb1/3p3p/1q1P3B/2N2P2/PP4PP/2RQRBK1 w - - 1 22} {polyglot: resign (illegal engine move by white: c4d5)}
{3rn3/6k1/R4p2/3P2p1/1Bn1r1B1/7P/5P1P/2R3K1 w - - 1 46} {polyglot: resign (illegal engine move by white: g8f6)}
{1n1R1rk1/1b4p1/4p2r/pp5p/4Np2/P3qB2/2Q3PP/3R3K b - - 5 31} {polyglot: resign (illegal engine move by black: f6e4)}
{8/5k2/8/5P2/5N2/5K2/8/b7 b - - 16 93} {polyglot: resign (illegal engine move by black: b8c6)}

[Bjoern]

Did you use pondering in the match ? I would not assume an error in matches without pondering...

[AndrewGrant]

I find it unlikely that Berserk has a sudden illegal move bugs, after playing hundreds of thousands of games without such. Getting the debug to see the string of comments sent to Berserk would be the path forward.