Yes. I did exactly what you requested. To the letter. No matter what I have done so far, it doesn't seem fix the glitch.
How does the newly installed game find the old saves? After installing 2.3.0, and then updating the "game" folder to 2.3.2, I started the game from the new master folder but found that the old saves were already there. I didn't have to transfer them. Even after I deleted 2.2.1 the saved files are still intact but now in the new game folder. I'm kind of confused as to how that works.
I'll try reentering the codes again too.
Okay for starters you have a separate 'save' folder on your C: Drive within the Users folder. The path looks something like this.-
I blacked out my name so as not to confuse you. Expect to see your name there. The numbers after the island may be different also. That folder (in this case, island-1499865023) contains all your saves, same as the 'saves' folder underneath the game folder of your installation of Holiday Island. Now here's where it gets a little tricky. The game initially reads the save files within the island-xxxxxxxxx folder as shown above,
NOT the save files within the 'saves' folder under the game folder. Why? I don't know, it is what it is.
So try this. Go to the island-xxxxxxxxxx folder under the renpy folder as indicated in the pic above. 'Cut' that folder, not delete, and then paste it somewhere else like your desktop, a thumb drive, etc. Doesn't matter, we just want it gone from underneath the 'renpy' folder indicated above. Now start your new install of Holiday Island and try and load one of your saves. The game will only be able to find a save within the saves folder underneath the game folder as we have removed the island-xxxxxxxxx underneath the 'renpy' folder indicated above. Don't worry, once it loads the save from the 'saves' folder, it will create a new island-xxxxxxxx folder underneath the renpy folder like before. That may solve the issue as your save files within your current island-xxxxxxxx folder may be corrupt. If that doesn't work, I am out of ideas.