It happened in two matches and seemed to be both when the enemy got the first shot and when they didn't. The damage seems to be fine now so I guess force closing and restarting fixed it?
Edit for clarification: my rifleman were level 3 then promoted to level 4 without closing the app. I then played two matches with the above stated issue. I force closed the game and when I reopened the app later, the damage seemed to be at appropriate levels.