This is really, really weird.
I STILL cannot reproduce it, not even with the save states.
I load save state #1, walk to the same spot you have in save state #2, and it doesn't trigger for me.
I tried walking like crazy to adjacent screens, and nothing. I just don't get any corruption in the automap.
If you can, could you try doing something for me?
I know the corruption from the save state is causing an extra tile to appear in the PPU, maybe you could try setting a breakpoint and sending/posting a screenshot of what the debugger pops up after the break.
Basically do this:
1) Open the ROM normally,
2) Open FCEUX's Hex Editor by going to Debug -> Hex Editor
3) Once the Hex Editor is open, go to View -> PPU Memory
4) Now, once in the PPU, press Ctrl+G, a little window will open asking you for an offset, type 20DE. That should bring you to the PPU address that corresponds to the area where the corrupted tile appears.
5) In address 0x20DE, do a right click. You should see the option "Add Write Breakpoint to Address 20DE". Click on that one, and the Debugger should automatically pop up, with the game still playing in the background.
6) Now, load your game and try to reproduce the same corruption from the one in your save state (where the extra tile appears next o the automap), or simply walk around until that extra tile appears next to the automap.
7) Once the corrupted tile is set to appear, the Debugger should automatically be brought up to the forefront, and the game will be paused. Take a screenshot of when this happens, specifically of the data in the Debugger.
This is where you should do the right click at (the 24 at 20DE):
That should pretty much give a clear indicator of what is going on.
If you happen to reproduce it, and the breakpoint works and the debugger pops up, send a screenshot of that. That should help a lot!