Just out of curiosity, what model knife is it? Although they claim 15 deg…. few really are.
I’d recommend the “measure twice [strike]cut[/strike] sharpen once” rule first… make sure the blade is properly clamped (vertical), that you’ve measured the angles correctly, etc.
Also, I’d check and make sure the edge is centered (symmetrical). It’s easy to tell usually by looking at the heel from the edge side, and the tip from the spine side. If it’s not sharpened even angle wise, it may not be.
From this point, you have a couple of choices. You can “sharpen out” the unevenness, working both sides to keep (or make) the edge symmetrical… so check as you go.
If it’s a buddy you sharpen for regularly,,, then you can do this over time… just set both sides at 15 deg. (or whatever you want, sharpen the knife), and eventually you’ll even out the sides. In use, he probably won’t notice a difference. Or you can do it all at once, working whichever side most to line up the edge and bevels.
Hope that makes sense… if not, ask… it’s probably me. 🙂