Our just turned 3 yr old scared us by getting her harness almost totally off on the interstate during our thanksgiving trip. She's in a ETA. When she first went forward facing we had a problem with her sliding the clip down but it seemed to resolve once we made sure she was all the way back in the seat. We tried this Wednesday and she's sitting back and the harness is tight. She only had a shirt on so it wasn't a coat making room for her to wiggle. This morning she even had her arms out again in the less than 5 minutes to Kroger. Any suggestions on things to check or how to keep the clip from sliding or any carseats with better clips and high weight limits. She's 38lbs and 39". I had noticed one of the times this happened the strap height had gone below her shoulders. Could something have broken and the straps are moving down when she's in there? We've used this seat for around 18 months with little problem.