I shoot Markins heads. I won't repeat what was already said about replacing the head- in this area you do pretty much get what you pay for.
You may be able to mitigate the problem by carefully balancing the camera/lens- if your Giottos has a dovetail clamp and lens plate that lets you slide the lens plate back and forth in the clamp.
For straight and level shooting, perfect balance is best. The mechanics of ballheads are such that when tightening the clamp the lens probably wants to creep in the direction it is heaviest.
For the moon, it should work better to make the package nose-heavy, relative to flat and level. As you tip a collared lens up at a steep angle the balance always shifts back to the camera end. Basic lever physics. Pushing the lens plate forward should rebalance it. You may find a "sweet spot" where the creep is at least mitigated if not eliminated.
I actually do this with my Markins heads, not to avoid creep, but to allow me to tension the head lighter than would be possible if it were not "un-balanced" that way. The moon, shot high in the sky as it should be, requires an unusually extreme angle you might never use otherwise, except maybe to shoot a bird high in a tree or some such thing.
I've never used your head, I'm just applying some general principles. Your head may or may not adapt to this balancing procedure, or it may even want something very different, depending on how the ball locks and what is causing it to creep.