After defeating Dealer Xy’exa in De Other Side dungeon (I think it happens during the flight back to the start of that section) the Focus target is cleared. I have seen this happen in multiple runs, that by the time I get back to Mueh’zala, I have no focus target.
More details: After defeating Dealer Xy’exa, focus is cleared when the focus target uses the Necrotic Distortion to transport to the start of the zone.