A somewhat dirty method is to change the "No Update" value to "Update" in the database. Have never done it myself, but I know it's possible. Another option might be to copy the UBE in question: If I'm not mistaken, you get the option to choose Update/No Update when copying a UBE.
We usually copy the report to a new update report. As Remo mentioned, you will see a choice to specify update report.
Now, if the report is referenced in so many places, you can delete the old (no update ) report and copy again the new (update ) report to the old name.