This season, before Christmas, Lerma has missed 9 games through suspension, that I can think of. 6 for an alleged bite last season, that there was no evidence of and 3 for a red that I think was 50/50. Personally I think the red against Coventry was unfair, Steve Cook was there, level with Lerma and in the direction of where the ball and player was going so it wasn't a red.
Other teams target Lerma and try to get him wound up. To Lerma's credit, he handles them brilliantly and is very clever and controlled, the Watford game comes to mind, when they targeted him and it backfired.
The referees have got it in for Lerma, it was even worse in the premier league, when the commentators loved mentioning his disciplinary record and never talked about his playing attributes and qualities. This season the referees have gone for us and against us, so no complaints overall. Against Fulham, Lewis cook should have been sent off and they should have had a penalty (if not for Harry Wilson's reputation of being a diving cheat).
I think there are players, like Ryan Manning of Swansea, who lied down on Dom in the penalty area and held onto Lerma's leg when he was trying to run to the ball and kicked our player off the ball, all without conceding a free kick or getting a yellow, who are much dirtier than Lerma, but they get unnoticed by referees because they don't have a reputation.