Basecamp will not transfer route to Drive 51 device but does transfer waypoints

Are you sure you're sending a route and not a track? Can you post an example here?

I am sending a route, I have no tracks, it is just a route up to North Carolina with a few waypoints.  Let me see what I can post that will help. The 2022 Fuge Device was my attempt to read a route from the Drive and then send it back to see it that would work. It did not. Let me know if you think of something that might help.

Difficult to know what's going on from those screenshots. Can you attach a gpx file of one of the routes? Is the software on your device up to date? Try a master reset to see if that resolves it. If not your device may be faulty so you'll need to contact Product Support 

I have two Drive devices and they both exhibit the same issue, waypoints transfer but not the route,

Running Basecamp version 4.7.4, software ver. 6.70 on Drive 51, maps are 2023.1

We really need a .gpx file of the route to see what's going on here as something isn't right.  Have you master reset one of the devices to see if that resolves it?

2022FUGE.zip

I did the master reset and transfered the route and the result was the same, all the waypoints are now on the device but not the route.

Thanks for the gpx file. It explains why there's an issue but you should have got an error message at least. The route is over 1300 miles and if routes are too long and/or complicated your Garmin cannot cope.  Try splitting the route into smaller chunks and you should find it works.