Ascent / Descent parameters for speed in Mission flights not behaving properly?


I am using a drone manufactured with a customized version of QGroundControl.
I have been trying to look through the parameters list and have been unable to find a way to resolve my issue, nor hear back from the makers.

What I have found behaviorally is that setting a speed in a mission seems to override the drones ability to match the desired altitude.

For example, I want the drone to climb 60m over a 200m distance and I set the speed at 5m/s.
Either because the drone is too heavy or for other reasons, the drone only manages to climb 40m and then directly ascends at the way point to the desired 60m.

This is undesirable for a number of reasons, so I am wondering if there is a way to either alter value that may prevent the drone from climbing faster or if there is a way in Qgroundcontrol to set a higher weight on the altitude vs the speed. Is there a way to set it as a 3D speed and not as the horizontal cruise speed?