Hello, so I don't know if the Gamcore version and if this version are the same, but on Gamcore it says 0.90. When I go to the Fire dungeon, from the save point statue, go up, to the right, continue to the right, go up through the doorway and head right until I reach the beach, you can get softlocked when you try jumping in the water. I had to reload my tab and go back to my previous save.
Please do not mention any uploads of the game here that aren't from this itch.io or the official Patreon page, because anything else are illegal uploads. So, we cannot help you with those anyway, because Spedumon didn't make any of those illegal browser ports. The problem you mentioned hasn't been reported in any of the official versions afaik, so it's most likely a problem with the version you came across.