I chose to not surrender my source and fight everyone. After I defeated everyone including Braccus in the final fight, the battle does not progress.

Dallis and Lucian are lying on the floor with 0 health with stunned and unconsiousness state applied and no further progression from there on. The game is still in combat state.

I can provide a savegame file from that exact situation for debug if needed.

I did this multiple times with the same result.

If there is something I still need to do to progess, it´s not clear to me in this state.