Character mistake: In the first call to a working structure fire Severide proceeded to head towards the basement from the middle level by walking down stairs but falls through. His first mistake was not checking the stairs with the halligan as any firefighter is taught, to check if they are sturdy. And last but definitely not least no firefighter should ever walk down stairs, especially wooden framed ones if they are on fire.
No Such Thing as Bad Luck - S7-E18
Character mistake: At the formal awards ceremony for Cruz the Police officers and Cruz are in dress uniform with their covers on. Serveride joins them on stage in uniform without his cover on and salutes Cruz. Serveride should have known to have on his cover for the ceremony. (00:58:00)