Dave,
The example you give is not clearly a button!
Are you simply typing your macro in, or using a custom editorTool Bar button or something? This append then occurs after you save?
If you can find out how to make it occur repeatedly try disabling you plugins on at a time until it not longer occurs to identify the possible cause.
Also check for system tiddlers that have being overridden for a possible error.
If this is occurring systematically understanding how it happens could be an opportunity for innovations.
Regards
Tony