My input is this...
You're crazy to run 8.5.1 for your dev server. Upgrade that immediately and make it work there and then move it to production. Problem solved.
8.5.1 was the initial release of XPages. Back in 2009. A lot has happened since then. Things have changes which is probably breaking something. Do NOT NOT NOT think that the almighty "Notes Backward Compatibility" is in effect for XPages, or any other web app dev system.
If your production server, and clients are on 9.01 - and that's awesome by the way, there's no reason in the world to have your dev server be 8.5.1.