Aric included a bunch of fixes from the bugfix patch. The modification system itself has been changed quite a bit. I think the version of the bugfix Aric included contained some core changes to the rules for mods. (The relevant change is how numeric indexes are used)
In my mod, open the 'scripts/Mansion.gd' file in any text editor. The first line of text has the number 32 written twice. Change both of those numbers to 31 and then try to install it.