Ex won't stick to pickup schedule, I'm missing work

This has been going on for 3 weeks now. We agreed on Fridays at 5pm for pickup, but she's showing up at 530 or 545 most weeks. I have to clock out early or just leave my coworkers hanging. I've texted her about it twice and she says traffic is unpredictable. I get that, but I can't keep losing 30 minutes of pay every week. Do I need to go through my lawyer over this or am I overreacting? We're trying to keep things civil for the kids.