Okay so I am not sure it's exactly what you are looking for, and it's only one fight, but Halicarnasus in Haukke Hard has issues due to ilvl/potency bloats, but this is mostly an issue while sync'd, she will summon an add, and you need to get the add to 1 HP as quickly as possible, after a period, she will eat the add and use an AoE based on how much HP the add had left, if you burst down her HP too quickly, she will summon the add, immediately eat it because you hit the health gate on her next mechanic and she wants to move things along, and wipe the party with a full powered AoE, so you either need to consciously hold DPS as soon as she starts summoning the add until it is targetable, which is unintuitive, or for the Tank to use LB1, which will be enough mitigation to survive the full power AoE, but unfortunately not all Tanks are aware that's even an optimal choice there, and I don't blame anyone for not knowing/remembering.
That said Haukke Hard is very unique about this, I have experienced wonkyness while Light Farming for Zodiac relics, like Shiva randomly starting phase transition at 80% HP and I do not understand what makes her do that especially because she only did that a portion of the time, but that was never a big issue, and I can always go bully Bahamut in T12 instead.