It seems odd that I am alerting some enemies despite my sneak being about 125, with Nightingale boots, Muffle spell, and Invisibility. Some enemies seem to have scripted moments when they are alerted. I don't it's an issue with my sneak skill; Draugr don't pop out of coffins and I can run circles around Falmer without alerting them. Just occasionally, some enemies seem to be aware of my presence even though the indicator is completely closed and I am invisible.

Has anyone else seen this?

ETA: They aren't attacking me or searching for me, but they are in combat mode with weapons/spells out despite there being no discernible threat.

i think sometimes it's just attached to proximity like with some dwemer automatons activating at the end of a zone/dungeon or by doing an action to procede further like lowering a bridge which would cause enemies to be alerted regardless of spotting you

can't think of any specific examples except for the blind bandit in the cave just east of Whiterun who initiates dialogue if you come too close

Yeah I've had those kinds of interactions, but these just seem to be pretty arbitrary.

It also cracks me up when someone makes a beeline for me and initiates dialogue even though I'm invisible

The other day I was working my way through a bandit cave, and dropped a couple of mammoth tusks in their dining area, just to see if it'd provoke a fight. It did - one bandit went right ahead and attacked another, then went back to his meal.

Then another bandit went over and pocketed one of the tusks, walked over to where I was crouching, still fully hidden, said "you should be more careful with your belongings", tucked the tusk into my inventory and went back to his patrol.