Calculation of gradient between waypoints

Hello,

This is a continuation of an issue, that I had and posted about already. I originally thought it was due something else, but I believe I have narrowed it down.

My flight plan consisted of waypoints containing negative heights. This is because I use relative height to myself and I am on a hill range. I fly down a slope to the beach.

I notice the Plane calculates a gradient to fly down the slope nice and smooth. However, on the return trip, it climbs very aggressively and then levels out at the point of the waypoint at launch. It then flies level back to the waypoint instead of a nice gradual climb.

I think it is because the calculation is using negative numbers and for some reason, does not perform the gradient calculation correctly. I think I could overcome this by using a different height setting in the plan like AMSL, so I do not have negative numbers.

Would I be correct in saying this?