Part of the Furniture
Thanks for the suggestions! I've never downgraded a Merlin firmware version before. How would I go about the process and are there risks involved of potentially bricking the router if it goes wrong?
Should be no different than upgrading. To be safe you can do a WPS button factory reset - minimal config just to get in - downgrade - WPS factory reset again.
Once in you can select "format Jffs on next boot" and restart again, though that may be redundant, I believe the WPS reset does that but can't hurt.