On new 2 stroke engines it happens more. The cylinder on 2 strokes non-rings nitro engines are tappered.

Sometimes you'll flood the engine a little bit..cuasing almost a freeze lock.
So when you press the electric starter's cone againts the spinner, it'll loosen the spinner and prop a little bit at a time.
As stew stated...don't have the engine at TDC when using an electric starter.

if you're going to use Loctite...DO NOT USE RED.[X(]
Use Blue.....