Having trouble with one of my Plopper 75's running on it's left side on retrieve. The right eye is almost straight up, when moving.

 

Anyone have any success tuning them? Looked everywhere and can't seem to find any answers. Have added a small split ring and barrel swivel, and didn't notice any change.

You might be reeling too fast.

Slow your roll.

A-Jay

I found mine were spinning sometimes on retrieve, no matter how fast or slow I went. I solved the problem by using a double swivel on the front eyelet instead of a split ring. Keeps the wonky spins to a minimum.

If it is laying on it's side or actually spinning, there is friction between the prop and the shaft or the bearing. I find the QC not to be the greatest, but most issues are an easy fix. 

You could try twisting the wire where the rear treble is attached. Start with maybe 1/4 turn or less and see if it doesn't make a difference.  If the body isn't spinning, I wouldn't mess with it though as an eye facing down on a topwater is actually a good thing.  I've added one to the belly side of a number of Spooks and when I get a strike on those, the bass really hammer them.