How wet is too wet for dry ice hash storage?

I've been doing dry ice hash for a while now without any issues, works great.

My last batch I thought was dry enough, but I was apparently wrong. Found a few mold spots.

How are you guys telling if your stuff is dry enough? I use the hygrometers to tell gauge my bud, is the same method useable for hash?

I am really hoping I can avoid the super dry, rock hard hash. I like it somewhat pliable