red flags us citizen

Im a us IMG I want to know What are the red flags? what are called massive red flags?

I am a IMG and a us citizen I'm done with step 1 and got a score of 252 and preparing for 2nd step I have red flags in my 2nd year of med school had to repeat it.Is it going to be a problem if I want to compete for good program in IM or gendral surgery. What are my chances in other specialtys...