Upgrade from 3.3.19052 to 3.4.19274 was fine!
All navigation voice commands working now.
Many thanks for your great support!
PS In the mean time I talked to 3 other friends being in 3.4.20196 and they have the same problem as me (they can not set any destination by using navi voice commands). They get the same response (“Navigation is still loading - Try again later”). Seems to me it may be a 20196 bug…
In case I upgrade to a higher version and want to go back again to 19274 can I do it directly using SynUpdater or do I have to go back to 3.3. again?