Magellan N509 Loses Signal While Driving

I have a Magellan G509M-7000 GPS that was a recent gift. I have an older model Magellan that has been essentially flawless, but this one is very annoying. It seems to lose signal after driving. I initially thought it was a minor connection problem, but the issue exists on three different vehicles. The power cord appears to have the antenna built parallel along it although the included instructions are of no use and searching online gave me no results. I tried repositioning the cord to see if it helped but I can't say that it made much difference. I can be driving along and find the cursor puts me on the grass or showing speeds nothing like the ones I am driving. Then after a while it "catches up" to me and seems fine. Sometimes it says "searching for signal". I noticed it even loses signal whenever I travel under trees. I never recall any problems with my other unit.