Receiving string in Serial, issue. Unity -> Arduino

Question

I'm sending a string via serial from Unity to an Arduino Mega with a baudRate of 115200. That string is parsed into an uInt_8 array and send to other arduino via i2c in packages of 12 bytes. This works great but only for the first 10 bytes (0-9) so it must have something to do with two decimals (10, 11). The string for 24 bytes looks like this ,0,255,0,055,0,025,0,255,0,etc. The values are always between 0/1, and 0/255.

void loop() {
   int serialIndex = 0;
   if(Serial.available() > 0){     
     while (0 < Serial.available()) {            // loop through all the received bytes 
        String bufferString;
        uint8_t bufferInt;
        bufferString = Serial.readStringUntil(','); 
        bufferInt = bufferString.toInt();      
        serialBuffer[serialIndex] = bufferInt;  // put current index byte in array      
        serialIndex ++;                          // add index. 
     }     
     sendBytes(); 
   }
   delay(50);
}

void sendBytes(){
    for(int i = 0; i<boards; i++){         
//        int i2cIndex = i*12;
//        for(int j = 0; j <12; j++){
//          i2cBuffer[j] = serialBuffer[j+i2cIndex];
//        }
        Wire.beginTransmission(i+1);
        Wire.write(serialBuffer, 12);
        Wire.endTransmission();  
    }
}

Answer 1

Thanks for the nudge in the right way George Profenza.

I've changed this:

if(Serial.available() > 0){     

to this:

if(Serial.available() == 30){     

I also lowered the send frequency in Unity but i'm implementing a handshake now between arduino en unity for better speed and efficiency.