@Tom-Cat Memory leak problems can be excluded (temporarily, obviously) by killing the app completely, i.e. get the list of running apps with a press of the system Overview/Recents button and swipe MRA away to actively kill it. That guarantees a clean start for the app next time. Just minimising/maximising the app won't clear the app's temporary data.
Rebooting does the same, but for all apps - it just takes a lot longer.
Another way I've seen the same 'Something went wrong' message is by trying to start navigating the route too quickly - before the app/comms is ready.
That doesn't seem to be the problem you're seeing, but just in case - give the app a chance to initialise itself straight after you've opened a route, i.e. let the background screen contents settle. It can be 5-10 seconds in poor reception I've noticed, but on a re-try it usually recovers and starts navigating.