Thanks for mentioning this was weird for you! Always interesting to hear what’s surprising for folks. The reason a goal will typically recommit immediately is when you change your data in a way that puts you on the wrong side of the road for yesterday. This might involve adding data for a do-less goal, or removing data on a do-more goal; because the graphs are almost all cumulative, it can happen even if you enter or remove data from weeks ago, because that still drops the whole line of your data down from that point, or pushes it up since that point.
So the current criteria for derailment is “in the red yesterday”. It used to be “two red days in a row”, but this actually created a loophole and was just not a great idea.