Hello Eduardo,
I have the same problem you do The NVC has rejected twice my wifes birth certificate from Colombia she is from Cali. I live in the state of Georgia and is so frustrating she had to fly back to Colombia today from Panama where the embassy is at and she is gonna find out about her birth certificate becuase the message I have recieved twice is part of this document is missing or is hard to read. please feel free to contact me if you want my phone number is 470 549 3433 I have whatsapp or my fb is ricardo woodman. Every time they reject a document is 1 month of delay.