Same issue in a file with 3 Player Avatars and 1 AI companion. We tested the bug by attempting to change the speaking order in Fort Joy Dungeon, under the Fort Joy Square waypoint.
After a fight surrounding a dying NPC, you get a key to unlock a nearby door. Opening this door immediately initiates a group dialogue and, as always, the character who speaks before the AI gets cut off as soon as they select their dialogue option and the AI instantly voices theirs. We created a quicksave right before this door.
The only "fix" we managed to find was our Host taking control of his companion to initiate the party dialogue. This allowed all of the Avatars to select their dialogue options and have them voiced successfully, but the AI companion says nothing.
The issue seems to be due to the fact that AI dialogue options are selected and voiced instantly. Players can cut off other players' lines by selecting their dialogue option too early/during the dialogue option that's currently being voiced.
Some possible fixes:
1. Force AI companions to always speak first
2. Disable AI dialogue (not great)
3. Add a (continue.) option while player dialogue choices are being voiced to prevent the AI from auto-skipping whoever ends up speaking before it
4. Find out why AI dialogue options being instantly selected and voiced functions the same as a player selecting their choice while the previous line is currently being voiced.
