Hi, I've got a 21 month old daughter, who has a knack of getting out of the pushchair when she's fully strapped in.
I've got two push chairs, each with a 5 point harness and she can do it in both, she just pushes her arms out of the straps and brings her feet onto the chair and stands up. I usually have to then pick her up before she falls/ climbs out. She's ok being put into the pushchair, and she will sit in there ok until something catches her eye/ or she gets bored (e.g. on stop in a queue).
Any other mums with the same problem? Did you find a solution.