I won't say that I don't make mistakes but 50 waypoints ! ! what on earth are you doing ? I can do northern Spain from the UK with not more than about 15 waypoints.
The gross error check at the end of the input is the distance from the plog to the GPS normaly the differance is one or two miles.
Remember that the SID,s & STAR,s are in the box so that part of the set up is easy the STAR on the taxi out and the SID when you get the arrival clearance.