I'm with Regis in the underground dungeon and I'm supposed to place bait in four tunnels. However, there are two tunnels where I cannot place the bait -- I can see where the bait should go but I can't interact with the spot.

Has anyone else had this problem and is there a way around it? I'm completely stuck at this point and can't continue with the quest. I've tried approaching from different angles but after an hour I give up.

I've played the game twice before with no issues so this is clearly related to the "updated" version of the game, which has caused me no end of trouble.