HGSS "level script" help

I want to make a script that activates once upon entering a specific map in HGSS. I noticed that all of the level scripts are empty, but the maps that have scripts that activate upon entering a map use the "MecScript" command in generic scripts in SDSME. These scripts don't have flag checks anywhere, so I don't understand what makes them activate only once. I also don't understand what gives one MecScript script priority over another one. I tried adding a self-made mecscript to new bark town, but when you leave your house, the game crashes. I tried adding a self-made mecscript to a different map that didnt have any of them, but it simply doesn't activate. If anyone could explain these things to me, or perhaps provide a template to make it work, that'd be great. Thanks in advance.

I have the same problem like when you leave the house the game crashes, did you found any solution?