NV+ 4.1.10 upgrade failed

I have had the exact same thing happen. Ready NAS NV+ v1 working fine for weeks with 4.1.9. Did the upgrade to 4.1.10, stuck in endless boot cycle. I spent 2 hours on phone with tech support; after trying several ideas we discovered that it would boot if disk four (just happened to be the first disk we attempted to boot without) was not installed. So, tech support declared a bad disk and said to replace it the case number was case #19515186. I thought it was quite a coincidence that I would have a disk failure at the precise time I was rebooting after a firmware upgrade and that we wold pick the "bad" disk on the first try, but I had no reason to dispute the call. Ordered a replacement disk 2nd day shipping; installed it -- hangs on boot again! It will still boot with only three disks. So, I re-installed firmware v. 4.1.9. No luck...it will now boot with four disks installed but it fails every time when trying to sync disk four. I have tried the new and the old disk with identical results. I could surely use some help - fortunately no data was lost but there is no redundancy now.