Our Frontier 85's harness strap keeps getting stuck. I've taken it off and it seems everything is on track. but if we loosen it and tighten it seems it tightens to a certain point then stops, and it's darn near impossible to get any tighter. Anyone else have problems? What can I do? It's usually just before it's tight enough and DH has to jerk it a few times forcefully to move a little.