Spiking occurs when your controls use pots that are dirty or otherwise cause un-commanded input.
Basically you can hold a control steady and the input from it can randomly 'spike' up or down, even though you haven't moved it.
As for a dogfight approach, I just had a great one today, and then I botched it by kicking too much rudder. 20mm everywhere!
It happens to everyone, so you need to do some analysis and see what's happening.
Can't really help you much without a very accurate description, or better yet, a video, other than to suggest things for you check out.
So, start with your controllers and see if they're causing you some trouble