Sounds to me like your jerky dehydrated at a constant temp of 160 was too high.
It had hardened the outside too fast for all the moisture from the inside to dehydrate slowly out. Trapping the moisture in.
Ziplocks are great for short periods of time. Around here long term storage isn't a problem. The jerky is usually gone by the next day.
If you can in the future, for long term storage invest in some Silica Gel Packets. They absorbs up to 15% of it's weight in water vapor. It's FDA approved. Not expensive at all. So 1 packet inserted into a flavor sealed bag should keep your jerky safe from mold.
Mylar bags can also be used for storing jerky.
If your with me that's great. If not. Get out of my way.