I had created a few waypoints on my GPSMAP 64 and accepted the default waypoint names; 024, 025, 026, 027, 028 029.
When I got home and connected the handheld to the computer, I dragged these six waypoints into a list I had been working on.
Unfortunately, in one of my Basecamp older lists, there already was an 026 and 027.
The "new" 026 and 027 from the handheld did not overwrite the older 026 and 027 in Basecamp.
It just put a copy of those two old waypoints in my new list.
No warning text, no query of options to overwrite, make a copy, rename, etc.
I did not notice that they had the wrong coordinates until after I had deleted them off the handheld.
Basecamp should really have some sort of popup dialog when it sees the same names but different coordinates when importing data.
I think it automatically adds .001 to waypoint names when importing GPX files.
But it apparently doesn't do any checking when using drag 'n drop of waypoints from the handheld back into a list.