The imperfect tense is supposed to mean an action in the past was (and possibly still is) habitual, repeated, or continuous? I don't understand how that would imply failure.
If someone said to me, "je devais aller chez toi," I wouldn't interpret that as a person not going to my place despite some requirement. I would understand that as they were repeatedly or habitually required to go to my place.
If I used to work as a business man and I was often required to show up for business meetings, wouldn't I say "je devais à les réunions d'affaires" to indicate that I was required habitually?