I wonder, do they have text with each other?
I had an Act 1 issue in which Shart's audio was broken but other than that, it seems situational. I am currently play Astarion's origin, I had Tav-banter (when the PC says something and one of the companions replies) with Lae'zel in Githyanki content and some Shar/artefact related stuff with Shadowheart but apart from this it's mostly been Astarion and Gale happily chatting about Myconide necromancy, dusty halls and whatever comes up. With my Gale Origin it was the same but just the other way around.
I am enjoying it because I like the two chatting but I was wondering if it was an approval thing or just generally only the two of them latching on to weird topics.
I'm playing as Tav and situation for me looks like this in act 1:
Shadowheart had banter with Lae'zel, Wyll, Gale and Astarion - zero banter with Karlach and Minthara.
Lae'zel had two banters with Wyll, one with Gale, several with Shadowheart - zero with the rest.
Karlach - no banter whatsoever with anyone.
Gale, Wyll and Astarion - all working fine between each other.
Act 2:
Shadowheart is mute. (her new content doesn't work)
Minthara is mute.
Lae'zel is mute.
Karlach is mute.
At this point I stopped using male companions.
Act 3:
Ladies are still mute.
In conclusion - women are broken to hell and beyond. And before you say "maybe you just finished all the banter", no, I didn't. Karlach was mute from the beginning, same with Minthara.