Why can't you navigate while moving at a slow speed? There is nothing wrong with your GPS, and it also does not require a 5HZ unit, and it also does not need any new chipset, and it does not need a laptop either.
I have a very old Garmin-45 that I purchased over 12 years ago. A very basic unit, but a very good unit for the mid 1990s. I use it for sailing, and sometimes when there is no wind, and stuck in the middle of the Pacific Ocean, well, you are not going to be moving very fast, but the GPS track it just fine. It gives me my LatLon, my track, my waypoints, etc. Worked great.
Try changing the settings on your GPS, and try it again.