wondering how to prevent it and how to get rid of it once it occurs
Don't freeze it or put it in the fridge for long periods of time. Put it in front of a fan to help dry it off.
Freezing it isn't so bad, honestly. You just have to be careful how long and how you defrost it.
I found i get it if i leave it to set in the freezer too long..just keep checking ur chocolate till it sets and knock it out of the mould A.S.A.P then i keep in a normal refrigerator better if it's in a sealed container. You will find especially with a filling that if you leave it too long in the freezer the filling seeps out somewhere. I find that once it has got wet from condensation it really is ruined and if you don't eat it quickly you will see the marks showing later on from the water.