The Delemain voice is missing when speaking with him inside the HQ, note he was voiced in the Lobby. Only V's replies are voiced, all other sounds seems to be there like the flying drone noise etc. I never had this issue with the previous builds of the game.

I don't think it's build related. It can and has been happening randomly on several quests in all builds. The only quest that I know of where the voice has always been missing is when Wacaco (sp?) calls you to start the mission to drive the guy who wants to kill a prisoner being transported.

I've played through that 3 times and her voice has been missing all 3 times.

I've never had missing audio with the Delamain one you're talking about including in 1.06.

Seems this has progressed into the Delamain Epistrophy's being glitched as well, whenever I get near one of the cabs I get a call from Delamain that I can't answer, nothing happens.

Just now I got near the Wellsprings Cab, and it doesn't progress any further nothing happens when I scan it, can't call it.
Seems the Whole Delamain questline is glitched, I didn't have any issues like the voice missing and it worked fine during the Delamain Epistrophy missions in the "day one patch" he'd call me say a cab is near etc. But now I get a call and it doesn't progress further.

I have had exactly the same symptoms with Delamain. I *think* that I have reported it with all the saves.

(I think, because the report page lacks any form of success or failure confirmation - it might as well send all the reports to /dev/null.)

The missing voice bug can happen at any time and anywhere, not just during the Delamain quest (in my playthrough, all his lines were voiced). I'm playing on 1.06 too.

I even once had a bug where all voices stopped playing. NPCs no longer said anything, no voices during phone calls, merchants have no voice, etc. I had to restart the game to get the voices back.