Issue with Permobil power wheelchair tipping forward on declines. Any advice?

My mom has a VERY expensive, custom Permobil power wheelchair that the PT fitted her for. Well... we are both terrified to use it now after we discovered it tips forward on simple declines! When she is on it, it seems to be incredibly top heavy. We have the sit leaned back when going downhill too. And by downhill I mean the 5 degree grade on most pedestrain curb slopes and the ramp in the wheelchair van.

Now we just use a regular wheelchair. We are waiting for NuMotion to decide how they're going to deal with this.