The lead paragraph transform sometimes moves content incorrectly.
Old example: Compare https://en.wikipedia.org/wiki/Arthur_Conan_Doyle and https://en.m.wikipedia.org/wiki/Arthur_Conan_Doyle. The two lead paragraphs are out of order on mobile, and the second paragraph appears above the infobox on small screens. There doesn't appear to be anything odd about the wikitext.
Report courtesy of jlebar on IRC.
New example: https://en.m.wikipedia.org/wiki/Surtsey
=== QA Steps
Please do all steps on beta cluster. Beta Cluster is configured to load articles from English Wikipedia when those are not present locally.
 Please verify that Surtsey has first paragraph aligned correctly. The article should start with bold "Surtsey"
Beta cluster - fixed https://en.m.wikipedia.beta.wmflabs.org/wiki/Surtsey
Production broken: https://en.m.wikipedia.org/wiki/Surtsey
For reference - broken article on production https://en.wikipedia.org/wiki/Surtsey