1. The quest is marked active. After advancing to the middle room, when you need to speak with the Guildmaster, the active quest marker points to the opposite direction, i.e. to the entrance of the dungeon (the door at the back of Sees-All-Colours), not to the final destination. After ignoriing the marker and entering the correct door (showing no marker at all) everything goes fine, the marker 'resets' to the correct destination.
2. After opeing doors with dwarven crystals ("Find a way through the Doors"), there is a lorebook in a tunnel, which emits yellow, not familiar blue light).