I'm worried that the storyline for Vette might be glitched, but I'm not sure enough to report it as a bug. Malavai has dialogue options all the time, but to be fair I gain affection with him much more rapidly. That would be that, except sometimes I see the 'Your companion wants to speak with you on your ship' icon, then when I get back to the ship there is no 'Mission Symbol' above their heads, and I cannot speak with them.
It would helpful to know exactly at what affection levels the new missions become available for each companion.