That’s odd. I honestly don’t have much issue with it. I’ll hold the plane level with the yoke, wait for the speed to stabilize, and then trim to remove any yoke input.
Of course the plane is unlikely to stay perfectly level, but it shouldn’t dive or climb drastically unless you hit some sort of air thermal (you can tell when that happens because the pitch doesn’t change much, yet the airplane suddenly climbs or descends).
If a plane is trimmed and thrust set for say 140kts level flight, then if it starts to descend, as the speed picks up it will correct itself. Generally speaking, in most planes, in weather that’s not too crazy, I can usually keep most aircraft within 100ft of my target altitude without too many constant trim adjustments. The Comanche is probably the easiest.
However, this goes out the window with the Kodiak. That plane just like to go into steep dives or climbs by itself. It doesn’t adhere to the laws of physics! I’m sure that’s not the case in the real one though 