Unfortunately I do not, and afaik, no one does, know what triggers "New Player bug" If you dm me on the discord with a savefile and tell me the issue(s) you want fixed/looked at, I can help - in this case I can help clear out the duplicates, restore lost gear and levels (maybe) (and if not, add replacement that makes it like I did) and potentially some other things that may or may not need to be addressed. Other than recommending the discord route I would say do the "standard" "failsafe" type "debugging" actions you might do with any game backup save Delete the existing Data from the game-folder and local Appdata folder (ShopSim in appdata's "Local" folder), and then redownload the zip and extract it again - I recommend not downloading it to, nor extracting it on/to, the Desktop - I recommend that it be placed somewhere else, and preferably a place where you would assume you have full access to (read, write, rewrite, etc) - as well I often recommend games have their own drive, if you have multiple drives.
and with erased settings, I would often also recommend trying to use windowed mode, with a resolution in game, that matches your desktop resolution, Resulting in a borderless windowed fullscreen looking game, that is hard to tell is windowed. (this is unlikely to be factoring into the issue at hand)