I don't use this feature, but looking at the code, I am guessing the rotating icon come on during submit, which has a short Ajax timeout.
To use the long Ajax timeout (and display the horizontal time icon like in backup) change:
submit_center_first('confirmed'.$id, _('Create'), _('Create recurrent invoices'), false, ICON_OK);
to:
submit_center_first('confirmed'.$id, _('Create'), _('Create recurrent invoices'), "process", ICON_OK);
Note: this really needs to be configurable on a page by page basis rather than hard-coding it, because people keep running into this problem on various pages as their usage of FA grows. Or the timeout needs to pop-up an alert asking the user if they want to continue or cancel. Or ajax needs to check if progress is actually being made and eliminate the timeout.
Finally, if you get past that timeout, then php also has a timeout.