k.
It's due to torque roll...left wing rotates to the ground.
Ok let's give out some tips

1-launch with full power always. If your running a high kv motor 3000kv plus ...you're most likely turning a small prop = low thrust but high speed. Launches are very scary.
2-When you launch raise the left wing. Rotate the plane in your hand before you throw so you're not having to think about ....raise the wing.... throw firm etc.
3-I do know and have tried a diskus launch. I have a club memeber who can do this perfect every time. If I can get with him I will shoot a launch video.
I don't use it because I'm not 1100% sure of myself to not crash the plane due to a bad throw
4-Throw hard and follow thru...aim up about 20 deg.... On my Fj I can actually throw it straight up and it will go!!!

Cp