Preparation:

a. Create a spreadsheet;
b. Save it as ODS;
c. Tools->Share Spreadsheet;
d. Check the "Share this spreadsheet with other users"->OK;
e. Confirm saving the file;
f. Close it.

Testing:

1. Using file manager, double-click the spreadsheet to open in Calc.
2. After it opens, confirm "The spreadsheet is in shared mode" warning in Calc.
3. Using file manager, double-click the spreadsheet again.
   => It will not open the second time; instead, the already opened file should activate. In the menu Window, there is only one instance of the file (as expected).
4. In Calc, edit any cell (say, put "1" into A1).
5. Repeat #3 above.
   => The same expected result: the file is *not* opened second time; instead, already opened file should activate. Menu Window only shows one instance of the file.
6. In Calc, save the file (Ctrl+S)
7. Repeat #3 above.
   => At this point, the second window appears with this file, accompanied by "The spreadsheet is in shared mode" warning, again. Confirming the warning, there are two entries for this document under Window menu. One may see that these two windows are not just different views of the same document (as created by Window->New Window); e.g., entering something in B1 in one window will not show in the other, as would happen if these were normal views into the same document.

Now you can edit the same document in two different windows in the same application session, and if you alter the same range, save the first window, and try to save the second, you will get a "Resolve Conflicts" dialog.

This is totally unexpected. This is reproducible using OOo 3.2.0.