I updated straight from 5.10.8 to 5.10.16 to 5.10.22. Just used the updater app with XRN2 Prime.
Maybe the idea is just to skip 5.10.15. Or if you have 5.10.15 to first downgrade to 5.10.8, and then upgrade to 5.10.22 from there? Please understand it's just an idea, I haven't tried it........