Yeah now that they've given Karlach lovers a little something (Act 3 spoilers)
in the epilogue to smooth over her bitter endings
I think that Minthara is the character now in need of the most work. It's unfortunate that she's so bugged because I enjoy her voice acting. Not sure if you should submit a bug report because I have no idea how Larian anticipated the new Minthara option to run. You could try though!