My STBXH has kept to his side of the agreement for the past year but now he's got a new lady friend he is cancelling and rearranging (I am sure I mentioned that I am taking the kids away and STBXH has booked a holiday for after we get back rather than taking it when we are away for a whole month).
My eldest worked out the dates and keeps asking "why did he do that?" and my youngest comes back from visits very difficult (screaming and crying about everything he is 4) and then today my daughter has come back and taken her feelings out on me, a punch in the face and pinches, as she says she doesn't like the lady friend or Daddy as she (LF) has taken him away from her (DD) and Daddy always has an angry face when they are there.
It's heartbreaking. Poor kids. FWIW, I ended the marriage, STBXH is a deeply flawed person which I protected the kids from for most of the marriage when possible, they have since had a honeymoon period with him and are now realising for themselves what he is like because I can't cover his arse for him.