Oh wow, yeah. I also fixed that bug (The one where you become transparent) after the fight with the Entropy sisters (What the 4 girls are called, Notice how all their names are spelled with the letters from Entropy). Keep your save file, I added a quick fast travel system near the last floor so you can go back to the previous floors with ease if you missed anything.
The secret girls locations:
There is one in the first floor -> First area to the left
(The secret girl in this floor has a conversation with Gaille if you want to see it, it's in the place where you got the lantern [2nd floor, 1st area, door to the rightmost of the F2 1st area entrance, then across the other door.)
There is the one through the green door in the 2nd floor
There is one in the maze - (You can still meet her)
The one sitting in the staircase between floor 2 and 3 cannot be interacted with but she's the "boogeywoman".
BY the way, update's done. Transfer your save file to the new version.