At random when I'm using Invincible, Holy Symbol, Bless or Mystic Door, they'll last way past the set times. There's been no way for me to confirm how (or even when) it happens. The only resolve I've seen for it has to be relogging or reapplying the buffs. In case of Mystic Door, it mostly happens when I forget I'm not in a party - the symbol appears, but I'm told I'm not in a party. I create a party, spawn the door and after the set time has passed, the icon is still around, though the door disappears.
Sadly, no. Like I said, it happens at random. The Mystic Door happens (9/10 times) if you're not in a party and activate the skill. The rest? Pure luck I'm afraid.