No, this makes perfect sense.
After the update, the receiver was set on a transponder that is transmitting the wrong date/time information. The default time mode of the firmware is GMT - ON, This time was referenced and your receiver's date/time was set to this incorrect date/time.
The daily/weekly timers were now ready to occur as scheduled, based on the incorrect date/time. Changing the local date/time backwards in time does not adjust the next daily/weekly timer, because it is referenced to a date based calendar and not a day of week. Changing the local date/time forwards erases timers as the calendar dates and times are now in the past and are no longer valid.
You can avoid these problems by starting the receiver on a transponder that transmits correct date/time then switching the receiver to manual local time mode.
or
Disconnect the coax so the receiver has no satellite time reference after firmware installation reboot. Set to manual local time and save the correct date/time before reconnecting the coax.
By your description, I am not sure that you performed the highly recommended Factory Reset. This may cause operational errors!.
Hope that this makes sense.