Highkeep guards that see invisible?
 

So today I was killing guards at high keep. Once I got lots of swords, cast invisible on myself and ran to sell them.

I was with 20% health and passed close to a guard. He saw and killed me.

So I tought, ok invisibility just have dropped 10 seconds after I used it right? Typical of EQ.

Got a ressurection, cast invisibility and ran to the bank with low health because the cleric didnt care about healing me. At that time my eyes were fixed on the invisibility icon that didnt blink even once and I am 100% sure it didnt fade.

What happened when I was next to a guard? He saw me and killed me.

Is this supposed to happen? Or is it a game mechanic I never learned?

Possibility is someone cast see invis on them

What are the chances of this to happen?

I remember it happening on and off when green first dropped, I don't really go there anymore.