[pengrus]

Dave,

Thanks for sharing the details. Have you considered to use a fresh new 4.1.5 database, plus fresh new 4.1.5 files, then import the (1) customer accounts, (2) orders into the new database, then add the mods back in?

Looks like you are upgrading with old database patched to new database + fresh new 4.1.5 files, then add mods back in...