DD is 6 and 48 lbs and almost 48 inches. She has been in a harnessed Frontier in my Pilot (2006) for a while and switched to a Graco Affix in DH's car about 4 months ago. She does fine in the booster in his car and would like to switch in mine. We tried our carpool Graco Turbobooster for a few days, but she has a really hard time buckling it. The belt locks up on her often, plus the booster seems to shift over the belt buckle when she gets out so the next time she gets in the seat is often on top of the buckle making it really hard. I hate having to help so much and she doesn't like it either.

What's my best best in this situation?
-Just leave her harnessed? But I'm not sure this issue is going to get any better with time/growth as she can physically reach and buckle without an issue, its just the set up in the car that seems to be the issue.
-Switch the Frontier to HHB mode? I haven't tried this yet bc I feel like I read bad things about the Frontier 85 as a booster.
-Buy a different booster? But will any of them ease this issue?