I kept an .esp as the base plugin for my mod. Today I updated it with CK 1.8, and now it's treated as an entirely different entity, effectively negating everything in it and all dependencies. In short, it becomes a "replacement", not an "update"

It's still the same name. I also don't depend on anything new. All I did was update the script (added a few properties) and add two FormLists.

What's going on here? My save game already had too much items for me to remember. I do have the old version of that plugin, but since the script has new properties, wouldn't it be incompatible?