Shared views are more difficult to keep 'up' over time because you're always going to see increased competition --- more publishers are joining Humix and generating content that might be matching on sites your videos had previously been showing on. Alternatively, sites where your videos are showing might see a decrease in visits to the pages where your videos are matching.
The best solution to this is to keep publishing good, high quality content to Humix to share, and to use best practices with SEO on those videos.
You're going to see volatility over time, that's natural, because of the nature of 'sharing' to other sites --- you can't necessarily control how traffic volume looks on the sites where your videos are matching and playing.