Help! I told landlords of non-working security door.

I live in Minnesota and resided in an apartment building that had a security door. It didnt work and a person who i had a restraining order on got into the building and left strange things on my door. I notified the police and I also notified the apartment manager about the incident and made a complaint about the door not working. I found a safe place to move to and notified the manager that I would be moving because of safety concerns. The door was never fixed either. I moved out and cleaned the apartment very well. Then after I moved out I recieved a letter from them stating that they kept my security deposit and I owe them for damages. There was no damage to the apartment and there is none checked off on the paper. Can they keep my deposit if I went through the proper procedures and the fact that they never fixed their security door? They want to take me to court for some $400 that I truly do not believe I owe them. I believe they owe me for my damage deposit and my pet deposito

What damages do they claim?