Bluetooth signal returns 0
Serial.parseInt() has a timeout. If something arrives on the serial, or is left over from a previous transmission and hasn't been read yet, Serial.parseInt() will start looking for a number to parse. When that fails it times out (and so does the second one immediately after it). When that timeout occurs parseInt() just returns 0.

IMHO the Arduino serial parsing routines are very poorly written and should be avoided. I have some tips on how to properly read serial here.