In the past we had it that if a player didn’t check the hand-moderated relations then we’d correct the relations if something happened (or the players noticed at a later date) but not the impact of not noticing - eg not being able to attack as your relations weren’t at disliked.
I think that we changed (so that now we would do the edit) that but need confirmation from someone who actually played in a Grudge game where this was changed. Get back to me if you were in such a game please.
You asked all players to check on the turn when the allegiance is changed and I remember that someone either on one of the teams didn’t check and as such couldn’t attack a couple of turns later.
You did make a change on the results in a grudge game Aussies vrs USA1 but only after much griping by we hard done by Aussies and a kindly concession by the Yanks. We had the Corsairs attack Harad (I think) at a pop and the attack failed as the Cors were still at neutral. It was agreed to modify the relations and result after some “Serious” negotiations between all parties. Hope this helps.