Martin,
Paul found out that you are using a 2000 grit stone. , I also checked out the site, but I could not tell what grit measuring system they were using. A 2000 US grit maybe finer than an 8000 Japanese grit. If you are getting a mirror finish, then I think you may have a US 2000 grit stone. A 2000 Japanese grit will leave the surface a bit hazy.
Now my confession, I cannot use a leather strop without dulling a blade. Sure, it looks pretty, but I press too hard into the soft leather and it just rounds that keen edge. So, I don’t strop any of my blades. I will only sharpen up to my 8000 stones, and stop there.
So try sharpening it again, but this time, don’t strop the blade and let us know how it worked out.
Cheers,
David