The bug at the end of Fungal Grotto is still happening. You get back to the first room but you cannot progress to the boss fight. You can't set up the portal and you thus cannot spawn the final boss.
A group mate had a similar problem just last night. They were on quest, picked up the rock, etc. We got the final boss but the quest wouldn't complete. This happened with a different guy a few months ago too.
We had done all this stuff correctly. We scanned the dungeon a second time, and the rock was gone. Did another run and it worked properly the second time through.
Grand Master crafter, all styles and all furnishing plans known pre U41.
Vamp and WW bites available for players.
Shoot me an in-game mail if you need anything, happy to help!