Embed URI path changes by itself

Background - I am running a multisite installation, but need only one shared gallery installation. The gallery installation works fine by itself and it even works with the older gallery module. In fact - it works with the newer module as well, but there are access problems.

I am experiencing a problem trying to set the embed uri to the correct path. I choose manual configuration and set the path to /drupal_installation/shared/?q=gallery. 'shared' here is for the site that I use to install all modules. I am sure that this bug is popping out because of my 'interesting' arrangement. Nonetheless, I can change the path to the above and all is well. But when I do the next step - sync all users - the program changes the embed uri to /../shared/?q=gallery. This happens automatically, and is the same as the path it chooses when I use automatic configuration. This new changed path does not work.

Please advise as to how I can change the path to my chosen path permanently - even if I know where the path is stored - then I can hard-code it.