On this edit
https://pt.wikipedia.org/w/index.php?diff=38540603
I just replaced the "o" by an "a", but Parsoid removed a </div> from other part of the page:
http://parsoid-lb.eqiad.wikimedia.org/_rt/ptwiki/?oldid=38538929
Version: unspecified
Severity: normal
The more relevant test is http://parsoid-lb.eqiad.wikimedia.org/_rtselser/ptwiki/?oldid=38538929, but that shows the same issue currently. Investigating.
<div style="background: "#ccccff"; color: #000000;" class="NavHead">Cronologia de Mandela (1918–2010) ...
That <div> has bad quoting which cause the <div> to be parsed as plain text and somehow seems to throw off parsing and diffs. I haven't investigated why that causes diffs, but that should explain why the </div> is lost because the opening <div> is now unmatched.
Search for Cronologia de Mandela (1918–2010) on the page in Comment 1 that gwicke pasted.