I think so, after all you are both supposed to do what has been agreed by the court. Full stop.
Your duty is to stick to that arrangement and do everything possible to make the child/children available at the given times.
There is no expectation that you merely use the court agreed arrangements as a loose start point for private negotiations and changes in schedule... it’s not as complicated as that. Or as disrespectful to the court, if you see what I mean?
Mind you, it’s great if parents can resolve animosity and not need to go back to court to rearrange schedules as life changes and children’s needs shift (although it never seems to be about the children’s needs, always about adults logistics, humm!).
But I think courts are very much aware that some people don’t go away and behave well after a court agreement, and that parents can play all sorts of games messing around with the schedule and turning up / not turning up etc.
So you’ve tried being accommodating, making changes to be helpful so the children still get time with their father even though he can’t/won’t stick to the original agreement. And sadly, he has responded by not sticking to the new plan, that he instigated, and it rather looks like he’s messing you and the children around, playing power games etc. So yes, reverting back to the original agreement to try and get everything working well again is a good plan in this situation.
I’d write in an email to him exactly why you are reverting back, and make it sound positive ie getting back to a schedule everyone can stick to, making everything clear again, needing to restore routine in the children’s lives etc. That way you are clear that you are taking the high road and not behaving like him, playing power games etc. And you have evidence for if and when you go back to court.
Poor you. Why do some people spend all this time and energy on such negative behaviours?!