In a period of 3 days, 15969 events from page previews errored (61.7% of all errors for that period)
The errors were due to totalInteractionTime being logged as null.
Reproduction steps
- As an anonymous user visit https://en.wikipedia.beta.wmflabs.org/wiki/Main_Page?debug=true
- Hover over a card and disable the popups feature.
- Refresh the page
- When reloaded, you'll notice events get sent of the form
- You'll notice totalInteractionTime is omitted. It should not be. This will lead to an error.