I have a doubt like whether the SUM tool is not supposed to be active during the daylight time shifts or the upgrade process itself not supposed to be active during that time.
This is the reply I can provide you from the SUM guide.
Make sure you do not run the Software Update Manager during daylight saving time shifts. Otherwise, the update process might result in errors.
SUM tool can be active it's only with Ugrade activity.
What made you conclude on this ?
Regards
RB