Before I started this quest I happened to pick up a Aetherium Shard while exploring, however I'm not sure if this is the problem.

I have read the book which triggers the quest and it has lead me to Arkngthamz, I have cleared the cave, met the ghost lady, found zephyr and reached the summit. However the quest marker does not progress after "Reach The Summit of Arkngthamz" even after I have solved the puzzle and recovered the Aetherium Shard. Can't talk to ghost lady, quest doesn't progress.

I've tried re-loading my save at different points and removing different factors that may have effected it but I picked the previous Aetherium Shard which was in my inventory before the quest triggered about 8 levels ago so I can't go back that far and it is un-removable from my inventory.

Any help or suggestions would be greatly appreciated, I was only really doing this quest for the bow but it has peaked my interest now and I'd like to complete it.