Most of the data that your navigation GPS unit displays is provided by a 3rd party, in other words for the most part Garmin, Magellan, etc. aren't in the business of doing their actual map data acquisition. Inaccurate data is generally the fault of the base data from sources. One of the large ones is HERE formerly NAVTEQ and is the one that Garmin uses for instance.The 3rd party providers in turn compile data from a vast number of private and public sources. Therefore different brands of GPS navigation equipment could be using the same source data and have the same errors.
HERE has a page on their web site for users to update information, that is one way to get the updates into a future update on your device.
HERE - Map Creator
Shelby