The problem above is given as said by the overlapping maps.
Cant have 2 or more routable maps covering the same regions on gps.
Gps can freeze if there are problems with data written into it.
Although any brand of SD or microSD card should work without any problems, Garmin recommends using SanDisk or Kingston brand cards. Most SD and microSD cards work with out any issues however Ultra, High Speed (such as 133x or faster), or SD and microSD cards specifically used for high end or professional electronics might not work.