Last modified not recording

When I edit a document (upload a new version of a document) it doesn't set the Last Modified date. It happens this way editing the entry in both the front-end and the back-end.

Thanks Ryan for reporting the issue. I confirmed that it happens, but at the moment, I am too busy. So please wait for me. I will work on this issue during this weekend

Sorry for could not reply you earlier. We had a holiday and just come back to work this morning !

Tuan