I threw my Rand McNally away in the middle of its first outing. Like you it would freeze up. I called tech support and they gave me the run around telling me it was the area I was in. I pulled my el-cheapo Garmin out of the Toad and it worked like a charm. I now use the Garmin 780. I mounted it on top of the dash at the center of my steering wheel so I don't have to look sideways or down - just like the helicopter dash - well, almost!
I'm not even using the 2011 GPS that came installed in this DP as its too limited and clunky. I just mounted the Garmin in the same location as my last DP - top of the dash.
The newer RV GPS units don't require the outside antenna. They search out the 3 needed sats very quickly. With this unit I've never had a freeze up but sometimes it does want to take me on roads I don't want to go (I usually map out my route for the day or trip then compare it to the GPS)
Wish you luck in your search - Richard
2011 Itasca Ellipse 42QD; 2012 Buick La Crosse; Retired US Army MSG (20 years AFS); Evangelist; Professional Parliamentarian; Author