This is an imported issue, original reference WP-73, created on 18 Aug 2014.

The problem: if I update the post two times, each time differently, Undo for the first change will fail because of a merge conflict on the date modified field. The same with push if the post changed in the remote environment – there will be a merge conflict at date modified field.

Suggested solution: do not store date modified with the entity itself, take it from the commit date. The whole problem is slightly more involved, see the wiki.