No need to update Sentinel. I could upgrade using the old version of Sentinel. They have made the firmware download available during the last couple of days. You only need the new Sentinel for entering frequencies in the expanded frequency range, as Sentinel has frequency restrictions in its program, but you can use the old Sentinel to upgrade to 1.28.15 just fine. Sentinel has no control over what firmware version you download, its the scanner that do the compare.
I don't know who wrote that message that JvdK showed us but it is totally wrong.
/Ubbe