@Abedul
In the first place the cause of such errors can be your GPSMapEdit, because it's not sufficiently precise tool for this purpose.
The mp2shp can also affect the routing, for example if the files _config and _types are not configured properly.
Could you demonstrate your problem on a small example? (ie a small road network in MP > road shapefiles after mp2shp > output IMG after MPC with the routing problems)