We are two people playing throught the campaign in multiplayer and after getting the all the four parts for Astrolabe Larrel won't speak to us. According to guides Larrel should speak to us after returning all four parts.
At first we gave one part to Gelarith (Arboretum one, I think) and then went to find the others. After getting the two more parts we returned to Gelarith and gave to parts to him. Gelarith didn't talk to us anymore so we figured we were still missing one part - the one in the first floor. So after a while we found the the fourth part and gave it to Gelarith. After that both he and Larrel refuse to speak to us.
I have save where we had returned only one part, so we decided to load that and try to return the three other parts during same conversation with Gelarith. After an hour of re-playing we did that, but Larrel still won't speak to us.
I tried loading a save created before giving 3 last parts to Gelarth (1 was alrady given to him) and then created the first part through console so I could return all the fours pieces at once, but this too resulted in same stuck situation.
It seems that console command to move to area might work in my case, but wan't to the consequenses of doing that. I can't really test that until we have time to play. I know that at least, we lost the experience from talking to Larrel and giving the Heartstone gem to him.