What calls those functions? Snippets are not sufficient.
old_1AB |= ( ENC_PORT & 0x03 ); //add current state
old_2AB |= ( ENC_PORT & 0x03 ); //add current state
old_3AB |= ( ENC_PORT & 0x03 ); //add current state
You are doing direct port manipulation, whether you realize it or not, to read some pin states. Notice that it is the SAME pins that you are reading in all three cases.