I suspect that it's the issue of the extra buffs re-rolling themselves, still hanging around behind the scenes - usually called the guidance bug. Basically, you'd see what the game would tell you for the amount you'd add for guidance, but when it actually then performed the check itself, it would roll a fresh d4 - often resulting in you seeing a success (when it suggested you'd rolled a 3, for example), but actually fail (because the actual check only rolled a 1), or vice-versa. This *looks* like that old bug is still creeping in somehow, and I've seen others mention it as well.