Brian: Your XT2 experiment obviously didn't turn out well, and I perfectly get your frustration. You didn't mention having experience with previous Garmin devices, so I'm guessing this was your first (and probably last) experience.
As I mentioned in my last post, the XT2 was Garmin's first serious attempt to connect their devices together. Architecturally, they try to attempt this using what they call the Explore DB that exists in their Server Cloud. The problem with Explore is that it can seriously alter a route. If you read Garmin forums, it's been the source of endless mind-numbing frustration.
Most XT2 users fall into it without even knowing. During installation of the Garmin Tread app, your asked if you want to use external storage. On the surface, who would like that? Answer yes, and you go down a rat hole that many users regret. Knowing the history of Explore, I said NO when prompted in Tread. The only thing I use Tread for is Traffic/Weather alerts, and a really slick connection for my Phone to Headsets (I have both Cardo and Sena Helmets). That's it. Furthermore, I manually copy all my GPX routes (wired) directly from my computer to the GPX folder on my SD Card within the XT3. Of course, it's recalculated on the XT3 side, but no manipulation by any other layer.
I'm guessing Explore is the source of having all your routes messed up. If you ever want to get a degree in everything Zumo, check out the following website:
https://zumouserforums.co.uk/
It's a treasure chest of everything Zumo XT, and a must resource for anybody who owns a Zumo or is thinking about it.