It's the Z key or the Enter Key or the Left Mouse click being spammed as those 3 are the confirm buttons, in the "New Game/Chapter Select" it's made that if you click confirm goes directly through New Game, again, I'm lost in this as well as it does not happen when I download the game. When I search online about it in forums, most of the replies are about having a controller/gamepad on, which I don't think is the case, and about cleaning the Keyboard/Mouse, which, again, I don't think is the case, so I may be pulling the obvious here, but have you tried downloading it again and testing it?
Again, the only person I found with this same problem was in this thread: https://forums.rpgmakerweb.com/index.php?threads/everytime-i-start-the-game-the-...
It's not something inherently on the game so I don't even know how I can change it to make it work in a hotfix, what bugs me is how it worked fine before and now it's happening this.
I'll try to repost the game again, but for this, I need to check and hide the new parts I'm already working on it, I didn't even had time to check if they're still working properly and are not interfering with anything prior to them, so I'll be checking this and them re-releasing the game to see if anything changes.