You don't have to do a reset every time you want to retune the recorder, just in case such this one (retune lost when you power off) or if you find your recorder stuck forever with "UPDATE" on the display.
It's definitevely a bug in the firmware, but if you expect Sony to fix it ... good luck! This firmware was issued on december 2009 after finding out that all the machine were not working anymore with the DSO in Italy. They were even faster than Pioneer (the real manufacturer) to fix it, but after that there was nothing more (i.e. to fix also the Guideplus issue) and in the meantime Sony (at least in Europe) didn't market any new development/product in this area.