TalkChess.com

[Ed Schroder]

Without knowing which margins are used it looks like a classic case of search irregularities. Surely you can fix an individual case with a wider A/B window but it may hurt the overall performance. I am sure the SF team have done considerable testing here.

From my own countless experiments the old-fashioned way worked best after all. A window of 0.50 for the first move, then for the rest of the moves a small margin of 0.125 making an exception for score drops, the margin is set to 0.25.

But then again, mine is not a modern chess program, re-searches are very expensive due to a big fat old fashioned mailbox EVAL and thus I tend to avoid them as much as I can.