So I recently updated to the most recent version of SMBX2, and after I did such, a pop-up error has been reoccurring whenever I attempt to test levels or even play them in my game. I know it must be something with the custom NPCs and warps, because in the games that come with the installation of SMBX2 play just fine. Mine doesn't however. I'm creating a Zelda II styled game, and so, have been using custom graphics from Squishy Rex's community graphic pack things. However, none of the NPCs have anything custom beyond graphic changes. Even so, this error continuously pops up whenever I attempt to test or regularly play levels:

I've tried 1. Reinstalling SMBX2, 2. Deleting the level files and creating new ones, then placing the same NPC and block graphics into the new files, and
3. Looking on the forums for other people's posts on possibly the same topic, all multiple times, and have come up with nothing to fix the problem.
Anybody able to help? I've worked countless days on this game already, and I'm dead set on finishing it.
If anyone needs anymore information or I wasn't clear enough, just tell me.