be aware, as above check your route especially if you have plotted the route in kurvy or extra kurvy mode.
Good advice, as always.
The other time I have seen it go wrong (and this will apply to routes converted from tracks, too) is where the route / track from say Kurviger or downloaded from a third party, took a road - maybe a small track - that is perfectly rideable but is not shown on the Garmin or TomTom’s own map. The device will route you right to the last point it knows. It will then route you over maybe many many miles to the next point it knows, just because it has no other way of doing it.
Similarly, if the third party or Kurviger track / route takes what is now a one way street, the device will take you all around the houses (literally) just to avoid taking you 10 feet down a no entry.
Wherever possible, always check the routes you have created, especially those generated outside of Garmin or TomTom’s generic software or come to you from a third party, even someone you know or trust. Five or ten minutes spent in the comfort of your home or hotel room, might just save you hours of frustration in the rain on the road. Trust me.
Modern GPS devices are now virtually small personal computers, very powerful in their operation but sometimes quite dumb, relying entirely on the settings you have told the device to work to; it’s the P in personal. Sometimes the device will simply not be able to do what you have asked for, so it will do its best, even if that is just rendering up straight lines between A, B, C and D.
PS From time to time I download from third parties, often from German magazines, such as Alpenrider; as much for the practice as anything else. When looking at the tracks, it’s often possible to see where the bod made a mistake, doubling back to get back to where they wanted to go. It’s sometimes easy to spot where they drop off the route for lunch, coffee or to get fuel (if you just convert their track blindly, you’ll be following them) and once or twice when they have stopped off at what seems to be nothing more than some bloke’s house. I sometimes wonder if he gets pissed off with blokes on bikes sitting by his front door, scratching their heads and shouting at their Garmins.