For the Glory of the Legion Hero - Got to Ketchum All achievement, the second snail is bugged. When entering the secret underwater cave in Neltharion’s Lair, I am disconnected from the game. My mage is currently stuck there as he is immediately disconnected upon logging in. Cannot even hearth out. I have tried disabling all addons to no effect.
While I can’t help with the bug, you can at least use the Stuck Character service to get your character out of the DC loop.
https://us.battle.net/support/en/help/product/wow/197/834/solution
If the automated service doesn’t work, you will need to make a ticket. Make sure you mention the the self service option didn’t work.
I was finally able to get the second snail in the underwater cave on my shaman. Not sure if this helped but I let the game recreate my WTF folder. There is still some issue/bug in that cave in the water before you reach the landing (character drops toward the floor) where the snail is, but no disconnect this time.
I will use the stuck character service to retrieve my mage. Or file ticket if need be.