"On Overwatch" Penance and disconnecting/timing out

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Currently it is physically impossible for me to achieve this Penance achievement. I joined a lobby on Malice Difficulty and completed it from “start” to finish without taking any melee damage. However at the current moment I am not able to go a single game without being returned to character select during initial loading and have to reconnect to the session everytime.

This happened just now and i rejoined as the players were clearing the sewer segment of the Prison Assassination mission. Rejoined and completed the entire mission then on taking no melee damage only being shot but as the mission finished the penance did not unlock. How can i complete a “FULL” mission if I am being timed out constantly and can’t even play a full mission.