The number of total pageviews for nl.wiktionary is clearly wrong , those for earlier periods too. In July there was no problem with these numbers, so I guess something went wrong recently. The figures are also not in line with the number of unique devices (nearly 7 pageviews per visit is at least 3 times more than usual for our project; my general impression is that everything is fine except for the pageviews.
The numbers make sense to me, did you split by agent type? You can see a lot of spider (crawler) traffic: https://stats.wikimedia.org/v2/#/nl.wiktionary.org/reading/total-page-views/normal|bar|2-year|agent~user*spider|monthly
But not a lot of user traffic. Does that make more sense with unique devices? And pageviews per unique device is not the same as pageviews per visit. The unique device estimate is explained in detail here: https://meta.wikimedia.org/wiki/Research:Unique_Devices
@MarcoSwart it hasn't changed, but maybe spider traffic has been steadily rising. There's also an unrelated but confusing bug where the time period on the dashboard changes by itself, the fix for that is being deployed soon.
It sounds like everything looks ok when we consider the split, so I'll decline this task but feel free to open again if you find a problem.