I noticed two off-by-one errors during a playthrough.
1. Golem's core/sculptor bug: If the sculptor asks for 3 golem's cores, and you have 2, they take them, and you have -1 golem's cores.
The culprit here is an if-then statement that says >= 2 instead of > 2 or >= 3. (search for "3 golem cores")
2. Levitation potion bug: At the yellow pillar, if you have only one levitation potion, it doesn't ask if you want to use one.
The culprit here is an if-then statement saying "if levitation > 1" which should be ">= 1" (assuming you aren't forcing the player to save their only potion for later e.g. floating to the top of the spire)