Dev made a pretty basic mistake and put the checks in the if statement in the wrong order...
View attachment 2445365
the enemy_num > 1 needs to be first in order to short circuit the if statement before it gets to the problematic one... not after. apparently had the knowledge he needed it but not how to use it. as soon as enemy2 gets set, it never gets unset so it would be easy for him to not encounter it if he uses the same test save files.
In order to fix it you should use this tool
UnRen.bat
1. Put the .bat file next to the exe files and run the .bat file
2. In the command prompt type '3' and press enter to enable developer console then close the window
3. Launch the game and load your save then press shift+o to open the command prompt and type in "enemy2 = slime" without the quotes and press enter
4. press escape to close the console. Make a save to save the variable to your save file. if you rewind behind this point you will lose what you've done and have to do it again. You should no longer get the error message