I own about 25 JEMs, one of each Universe except I have 2 UV7BKs Green dot, some RGs and many JS
I'd say after a good setup one out of three plays great!
The other 2/3s need fret filing to make most of them play great.
One or two in ten have twisted necks and will never play great.
The worst and saddest JEM I ever owned was a GMC that had a twisted neck.
I sold it because it was unplayable. It was mint looking too.
I have a different GMC now and it plays great! It has a few chips but I'd rather have this one than the mint one.
It's hard buying guitars that get shipped to you without playing them.
Guitar stores with high end guitars are a thing of the past in most towns.