Can't edit Animations or Collections, blue cube with white document icon

[FZGames]

Hello,

I'm supposed to have a game finished in a few days and since 2D Toolkit broke when I upgraded to Unity 2018.3, I downgraded back to 2018.2 again, but I'm having a strange problem, where if I try to edit my animations or collections, they show up as the normal blue prefab cube but with a white rectangular 'document' icon on top of them, and Unity won't let me click the 'Open Editor' button, saying "Components that are only on some of the selected objects cannot be multi-edited". I can confirm that there is only one object selected, the prefab 2D Toolkit created. With Sprite Collections, I can select something which uses a collection and press the 'e' button to edit it, but animation wise there's no option to edit it without selecting it in the editor. I'm really stuck. I rolled back the files in GitHub even with no difference. What has happened here? Has some kind of reference been broken? I've tried Rebuild Index and Rebuild All Sprites. Please help.