Friendship Quest - 10 rep instead of 5

I've done the Friendship Quest many times, and I've noticed that sometimes I'll get 5 rep from the Elder when he repairs the pendant, and sometimes not. I can't see any pattern to it. I've tried it with my former squadmates back in squad, close by, and not get the rep, and I've gotten the rep when I was alone and they were far away. For a while it seemed like clicking the quest responses slowly made it work, but that's not guaranteed either. Is it random? Has anyone seen a pattern or detected a reason behind this behavior?

Just to avoid any confusion, I know that you always get rep when you turn the repaired pendant in to Chiah for a token of friendship. This question pertains to that interaction with the Elder when he repairs the flawed pendant using the stones.

Thanks for your help.