Hi,
Since over one year the Technical Wishes team of Wikimedia Deutschland has been working on an extension for an easier and less scary handling of edit conflicts. After a first beta-version (available since beginning of 2017) this week a new version is being rolled out as part of the branch wmf/1.33.0-wmf.3. This version introduced a bug which led to the edit conflict resolution page being shown when using the preview function anthrough there was no edit conflict. This led to edits being lost in some cases.
As a reaction to various reports about this (T208840 https://phabricator.wikimedia.org/T208840, T209012 https://phabricator.wikimedia.org/T209012, T209036 https://phabricator.wikimedia.org/T209036 and others), we temporarily disabled the extension completely his morning (2018-11-08 10:49 UTC). The bug was found and fixed and we plan to reenable the extension again at 19:00 UTC.
To our knowledge only users who had the beta feature enabled were affected.
Cheers,
Michael Schönitzer for the Technical Wishes team