this has been an on-and-off issue with the game for some time now, even prior to the Siptah expansion - disappearing health bars for thralls/pets despite being engaged in combat. now the issue appears to be that if you have 2 thralls following per the new “authority” perk, sometimes one of the thralls health bar doesn’t show despite being engaged in combat (not really sure if this is exclusive to having 2 thralls, but it’s what i’ve noticed). the topic search did not yield any open threads for this topic on pc so i elected to post this as a notification.
obviously losing track of your thrall/pet’s health can be significantly detrimental to the experience, as they might die.