You aren't the only one with the crazy fluctuations. The group of websites I monitor via Moz experienced DA changes from +3 to -17. The industry this cluster of sites is in tends to change mightily every time Moz refreshes - DA within the top players in the industry ranges from 20-65 on average. As long as the fluctuation is holding steady across the entire industry, we aren't seeing it as cause for alarm. We do see the same trend and same show runners each update.

My thoughts - as a whole the industry I am in is slipping behind the curve in keeping up with authority signals. The entire point of the tracking is so we can keep ahead of those things. Being proactive not reactive. Don't look at your domains as a single point. Get their competition in there too. You can see how the entire group is performing.