Seems the effect of "chording" has changed compared with a few days ago?
Suppose there's a number 1, and I've marked one positive mine around it, and there are 3 unopened cells remaining around it, which contain one positive mine and one negative mine.
A few days ago, when I chorded on the 1, one of the 3 unopened cells (the one without a mine) would open. But now it seems none of them would open.