Im not sure how it happens and it's not very often, but it occurs both in PVP and PVE. Basically, sometimes when a person (sometimes me) places a mist bomb it is invisible, but it still takes effect. So in vana, there is no shivermist on the window but the zombies and explosive jellies are still being frozen. This is more irritating in lockdown; i might run through somewhere which seems safe, but suddenly stop of shock because i cannot see the voltaic tempest or freeze on the spot because the shivermist is invisible. It becomes hard to play. Addittedly it occurs but rarely, but it'd be great if it could be fixed. thanks.
Do you have 'Cull Transients' enabled? Since that is often the main cause that off-screen effects won't show up when you get in range. I always turn that feature off in LD.