Help needed with Bug 60780

It works okay, except when you try to Save a Copy to docx, then:
 You can't open the copy file unless you close the original.
 If you modify the original and try to save it, LO will ask you if you
really
 want to save to docx format, regardless what's the original file's format,
 closing and reopening solves this too.

First patch that got pushed out:
https://gerrit.libreoffice.org/#/c/2829/

The idea here was to copy Save as, except the dialog title and call
storeToURL
instead of saveAsURL, it's in an unfinished state, but it works with the
above mentioned bug. I worked on it more later, but the situation didn't
improve,
so, I rewrote it.

As it currently stands:
https://gerrit.libreoffice.org/#/c/3355/

Same idea but with using export and a bit better execution.
The code works by, when a SID_SAVEACOPY request is received,
it sends out an SID_EXPORTDOC request with an SfxBoolItem set to true, to
later identify it in guisaveas.cxx at GUIStoreModel and OutputFileDialog
method.
The flags are set to the one that SaveTo uses, with the addition of a
SAVEACOPY_REQUESTED to set the dialog title in filedlghelper.cxx

Both patches have the same bugs, I have wasted quite some time trying to
figure out what's missing, so I would like to know if the problem lies in
my code,
or that docx saving isn't prepared for use with storeToURL.