Not sure if it would help, I never had the routes deleted without the maps, waypoints, etc deleted as well.

I sent an email earlier this year to tech support about that and their answer was the following:

"thank you for your message. Please make sure there is at minimum 25% memory left in your IOS device at every time.
Otherwise the IOS system is deleting "non-priority data" regularaly.
Often it helps to delete data that is not needed anymore, like pictures, videos, messahes, etc.

We are always happy to help if you have more questions.

Kind regards
Frank Woidich"

I then asked if it was possible to have iGlide as 'priority' data but never got any answer.