Welcome to the forum.
Is the 17/21 degree angles the original angles or after you have sharpened it on the WE?
If the answer is factory, then this is common to have uneven bevels on factory edges. This is the beauty of the WE is it will fix the uneven angles on factory edges. Even my high end knives have uneven angles/bevels. Just by “eye-balling” them I can tell they aren’t equal.
If the answer is after using the WE then, a.) make sure blade is centered (if the spine is square shouldn’t be a problem). b.) don’t work 1 side too much. Spend time on both sides.
I made this mistake more than once (don’t know if it is your problem or not). I was tying to raise a burr on my first stone. This was a re-profile so I had a good amount of steel to remove. I worked the right side until getting a burr, then the left. The result was both sides were 20, but uneven bevels. The fix is work both sides evenly. If one side needs more work you still have to give the other side equal strokes.
If this is the factory edge and the 2 sides are that far apart you may have a good deal of steel to remove to get them equal.