I think at one time Voln symbols being dispelled was considered a bug and squished. If so, its back. I've lost them to both bandit crystals and greater moor wight 417 in recent days.
CoL signs used to be the same, also; they were considered spell effects, and (now) show up in 'spell active'.
I always considered this a good thing, because anything that hit my Sign of Warding/crap 1-mana effect, was NOT hitting my Elemental Barrier/30-mana effect....