Well, I tried uploading yet another updated version of my project to Realms, completely stripped of the old datapacks it had when the Error (-1) stepped up in front of me and got in the way of things.

I'm sorry that I had to come back here much sooner than I usually do, but I'd like to try this thing out to see if I can finally join Realms again. (We're focusing on the Error (-1), by the way, just so I don't confuse anyone, hehe...)