It's not uncommon with those engines when new. Sometimes it's due to over-priming, sometimes it's a combination of a too-hot glowplug or too much nitro in the fuel.

Basically, the engine is just fireing a tad early as you flip it up on compression, so it turns around and goes the other way. Sometimes just flipping harder "fixes" the problem.

You can also just flip it backwards and the engine will run forwards.