I have a 205. Bought new 14 years ago. The inconsistent connection was usually due to the mini USB cable and/or the cradle or corrupt data on the device. Sometimes I literally have to mash the device to the cradle to get it to sync. Using several rubber bands to hold the 205 firmly on the cradle.
As JOEVANGENT mentions, all those tasks are good ways of resolving this, starting with the easiest items. I would just add after all of the above is to try a different computer, then buy a new Garmin.