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From a quick study into the EPERM issue, it seems having the game in the main program folder causes this problem. If you haven't already, try completely reinstalling the game and putting it somewhere else on your computer (putting it in Programs first before moving it can cause some read-only issues to persist)
Another potential thing to just check is... have you made sure to unzip / extract the game first? EPERM relates to not having permission for the program to 'write' changes, in this case to the persistent save file. It sometimes can't do this if you haven't unzipped the game first.
The only other thing I can think of that may cause such an issue would be, worryingly enough, some kind of malware or issues on your computer... so if all else fails it may be worth trying to do some computer cleansing.
Hopefully some amount of this is useful for you!
It sounds like a stupid reason, and it's a quirk of RPG Maker as an engine and not something we've done ourselves, but yeah... the game doesn't want to run if you have multiple issues of the game running at once.
I'm sorry that it was a nuisance for you, and I'm sorry it's something beyond our control and a bit unpredictable, but hopefully the game now works smoothly and you can enjoy it nonetheless.