Due to the « Week Number Rollover » (WNRO) it is possible that the Grundig navigation system shows a different date after 6 April. Occasionally it can also happen that other irregularities (will) occur.
The WNRO takes place once every 19 years. The rollover is a result of the internal satellite storage numerator. The numerator of these satellites jumps back to zero after every 19.7 years.
Irregularities that occur due to the WNRO, could be remedied by performing this firmware update.