Lots of problems and progression blocks.
After the first fight, you can progression block by returning to the previous screen. If you leave the area and return to the first fight map, it freezes the game.
You start off the game with a load error.
Lots of passability/layering issues, like the shadows.
The elder is apparently a statue?
If you enter the lava area then return, it keeps the tint and it resets the door so you have to fight the boss again.
If you talk to the starting crystal multiple times in the thunder area, it can permanently progression block you depending on if you saved.