Here is another thing that can go wrong. It "happened" to me a couple of months ago.
I wheeled my AI into the water, went back to the car to double check a few things, locked it and got into the AI for a "glorious" take off.
There was a good wind but the AI wasn't as swift as expected. Something was stopping it from picking up speed. As there were a lot of water plants, my guess was that some green got around the daggerboard or rudder.
I pulled the rudder up and down but no improvement. Got the daggerboard out and back in: still the same.
I turned around to look at the back of the AI and then I realised ......that the wheels where still plugged in.
Well, these things happen. As they say here in Belgium: The only people making no mistakes are those sitting on their butt the whole day doing nothing.