Board Thread:Support Requests - Getting Technical/@comment-14259279-20191230125649/@comment-9605025-20191230210354

Try using the classic editor source mode. That one shouldn't give you any issues. The fancier editors (VisualEditor and classic editor's visual mode) have had issues like this in the past. With VisualEditor, even though you are making the edit in source mode, the editor reverts to visual mode prior to saving changes. Therefore, if there is an issue with VisualEditor inserting random text while saving an edit, it will likely still happen even if you only used source mode to make changes. This is not the case for classic editor.