Have you tried entering the code, and then use trial and error on the last symbol to brute-force the door?
First, adjust the water-level to the highest level. Then get the Eye.
Second adjust the water level to the lowest level so you can get to the first room with 2 codes. Write down the codes. The number corresponds with the position of the door.
Thirdly, adjust the water level so you can reach the screen after the one you got the first two codes. This will give you the codes for 3 and 4. Write these down too.
Fourtly, whatever you do, you cannot reach the next screen, but you have 4/5 codes. Head back to the door.
Fiftly, Enter 4 of the 5 codes you found first, then keep jumping on the code you don't know to brute-force open it.
Sixtly, By having the eye, you should now be able to fall through the floor getting to the next part of the level.