At the end of my tether with my DP's ExW!
Consistently, she messes around with pick up/ drop off times and pretty much just does whatever suits her! Won't unlock or answer the door/ phone when DSS's are dropped off on time to her, which has often meant we have to drive them back to our home and rearrange our day. I'm lucky my employer is very flexible, but there have been times I need to be at a meeting over 3 hours away and then can't attend.
Anyway, I've had enough of it. I've had enough of everyone dancing to her tune. I've had to rearrange my plans (work/ family commitments/ activities/ time with DP) to suit her on too many occasions, and there is never a consequence for her except DP giving her a bollocking.
DP and I have always made sure we are on time or slightly early (not a phonecall when we are outside her house a hour early with no prior communication. But 10/15 minutes early and let her/ DSS know there's no rush).
So, next handover day is me doing pick up. Petty Polly in me is going to turn up whenever I feel like it. It won't change anything, she will still do what she likes, but it'll at least make me feel better that she's been negatively impacted for once.