This may be two different bugs but it could be related.
The unique belt “Harbinger of Stars” is not supposed to “cast Meteor on crit” by directly casting “Meteor” but it does, at least when using “Lightning Meteor” (Vilatria’s Downfall Set Staff). I have only casted Meteor (one at a time) to test this, there is nothing else that could proc it as far as I can see but additional Meteors are casted (and consume Mana). The additional Meteors are landing on enemies on different locations, not where the mouse cursor (original cast) is.
In addition to that, “Lightning Meteor” shows wrong FX. A few weeks ago it was pure lightning, now the downfall of the meteor looks like a fire meteor, but the impact looks like a lightning crater, see images below:
Lightning Meteor Landing
Lightning Meteor Impact