So, some invisible creatures that can aggro players use spells with SPELL_AURA_MOD_INVISIBILITY (instead of normal stealth spells) and they will not aggro with the aura applied.
Aura ID used to test: 16380
Creature ID used to test: 25484
Issue, how to reproduce ect: https://www.youtube.com/watch?v=cf5g6OqZKqU&feature=youtu.be
Proof these creatures should have this aura:

Branch 3.3.5, may be an issue on master as well, have not tested on master.
TrinityCore rev. 54c00ecca196 2020-01-12 17:21:21 +0100 (3.3.5 branch)
Confirm it happen also in 3.3.5 with this npc:
SpawnID: 79549
Entry: 20882.
Probably spells that use invisibility with misc = 0 must allow the npc to aggro by los
Did test in retail and they aggro?
@Killyana yes ofc, they do aggro on retail
@Treeston maybe this is somehow related to threat system?
Don't think it should be offhand. Maybe it just never gets MoveInLineOfSight, or invis is checked in one of the CanAIAttack/CanAttack/etc. checks?