In the last few days, API calls to user_timeline (with exclude_replies not set) started missing tweets.
We get the same result when viewing the timeline via twitter web.
https://twitter.com/tweepsmap shows our tweets on the 28th
But https://twitter.com/tweepsmap/with_replies only shows our replies on the 28th
Also, if you another user views the timeline they can see both, but if we view the timeline (logged in) the tweets are missing