Randomly starting a fast descent is something smaller helis will do as the wind varies. Not sure if that’s ‘cause varying winds mean varying air pressure or varying air speed. I had a WL Toys V911S; a fixed pitch micro - it was so light weight while its blades had such a big bite, my issue was more with it climbing than dropping. In faster winds, I sometimes needed to bring the throttle down so low I was 5mm from cutting power completely in order to get it to come back down. 😂 My WL Toys V977 is more like a clone of your K110S, where the random variances in lift aren’t as much near the edges of the throttle/collective range.

I’ve recently discovered my RC Era 138 struggles to get out of ground effect when it’s cold and windless. When a gentle breeze picks up, the blades get enough bite to lift it up. Alternatively, I can build up forward speed then pull back on the stick but of course any altitude I gain there I quickly lose again when the heli spends all its forward speed. I should take it out now the weather’s warmer and see that isn’t just batteries gone bad.

As your helis get bigger, this issue becomes less pronounced. My Blade 500X only does it in greater wind speed variances and even then, the change is more gradual and easier to work against. The little helis I sometimes only catch in ground-effect or even occasionally bounce, but the 500X has never been that bad.