I think your code is increasing mDegree by 0.5 each frame, and mDegree is the amount that you're rotating your object each frame. So after 100 frames you're rotating by 50 degrees per frame. Eventually, you're rotating so fast that it's starting to slow down and reverse.

Edit : Never mind - just noticed that you had a separate store for the original positions (mOrigins). Any chance that float deltaTime is incorrect, and is actually the total time elapsed?

I think your code is increasing mDegree by 0.5 each frame, and mDegree is the amount that you're rotating your object each frame. So after 100 frames you're rotating by 50 degrees per frame. Eventually, you're rotating so fast that it's starting to slow down and reverse.

Edit : Never mind - just noticed that you had a separate store for the original positions (mOrigins)

I think your code is increasing mDegree by 0.5 each frame, and mDegree is the amount that you're rotating your object each frame. So after 100 frames you're rotating by 50 degrees per frame. Eventually, you're rotating so fast that it's starting to slow down and reverse.