When getting the coral from block 6 level 2, the chest (in the secret alcove) that it is supposed to be in is empty. The chest looks like it has already been opened, and clicking on it does nothing.

I reloaded a previous save, and got the same outcome. I also tried clicking on the chest from every conceivable angle with no luck.

Has anybody got the coral successfully with GOG's release?

I e-mailed GOG support about this bug (and others) and they told me all of my concerns should be addressed in this most recent patch. That doesn't appear to be the case though. I'm hoping that this doesn't imply that they think this isn't a bug, because the coral leads to one of the best rewards in the game, and it's pretty important for 1980's mode.

It's still bugged in the current patch version. Hopefully a future one will address it.

Whelp, any way to hack the item into the game?

In a few minutes I'm going to post some solution for this bug. I hope it helps.

edit: here it is: link