When mining obsidian in a lava pool with water on top, if you mine a block below you while sneaking, there is a brief moment where your hitbox enters the lava below before the water converts it. When this lava converts to obsidian, you do not shift above it as you should. Instead, you continue to fall through it. This can trap players in lava and with obsidian above them. If they don’t have a fast enough pickaxe and good enough armor, they can easily die and lose all their items.
I would suggest fixing it by reprogramming obsidian formation so that it checks for player hitboxes in contact with it and shifts them to a usable block above it to prevent players from phasing under it and being softlocked into dying.
I lost an enchanted golden apple to this bug on my 600 day (so far) world. Please fix!
duplicate of MC-157636