I ran it by my L and he said don't worry about it. I give her regular and expected contact with my stbx - I am never late with drop offs or pick up. I know she loves the kids and they love her. I know they benefit from regular contact with her which I ensure she gets.
I just don't like being bullied on my time.
If she complains, I just say "yes this is what divorce is - it stinks and we lose half of our kids lives."