Traditionally, routes can be problematic if they cross over themselves and the suchlike, and conventional wisdom is to create eg 2 linear routes: out and back.
But I've found my edge 800 to work quite sensibly in this regard, although I do tend to create multiple routes still.
Crashing upon starting to navigate a route is not a 'known issue', to the best of my knowledge.
Is the crash repeatable?
I'd advise against using the thing in anger ( eg DIYxGPS ) before you've become familiar with it, but you know that now!
I used mine at first on regular local rides and commutes where it wasn't necessary, just to become familiar with it, so that I had good confidence when I needed to use it in anger.
Even then, the first time I was relying on it for navigation, I hit a 'known' ( to everyone but me ) bug and it crapped out! Fortunately a bit of fettling at the next control got things up and running again.