So, I have just returned to hacking Sonic 2 for SMS after a yearlong hiatus. All was going well, with me trying to revamp the original game to look more aesthetically pleasing, when I finished Aqua Lake Zone. When I built it the first time, it said something about the mappings for Aqua Lake 2 being done twice. Filled with anxiety, I reverted the changes to the mappings by copy-pasting in the mappings from a backup disassembly, and redoing things from there. Finally, I do it, but now I get an error message saying I have a memory overflow in Bank 21. I have not added any tiles or anything. Just changed what was there. I am unsure how I caused the overflow.