I've also noticed it is very easy for the AP to (correctly) disconnect if you fly too slowly.
Engine management and use of flaps takes practice and experimentation on approach.
Depending on weight etc., I'm having to drop a notch of flaps close to 200 kias,and further flap extensions causes massive drag... as does the airbrake. As such it is very easy to drop below the yellow bug -- which of course I keep forgetting to set by clicking on the placard.
It's challenging- but good fun - to fly.