SDI12 library doesn't display measurements with + or - sign in it

Question

Arduino library source: https://github.com/joranbeasley/SDISerial

The problem I'm having is when I'm trying to get the measurement from sensor using SDI12 I only receive first digit which is channel number of the device.

This is how it should work:

Master: 1M! (Measure)
Sonde: 10617[CR][LF] (ch1, 061s to measure,7 sensors).
Sonde: 1[CR][LF] (Measurement ready)
Master: 1D0! (Send data)
Sonde: 1+17.5+12.05+98.7+8.25+6.45[CR][LF]
Master: 1D1! (Send rest of the data)
Sonde: 1-325+10[CR][LF]

The only thing I'm receiving after 1D0! command is "1". I think that it must be because of the + - operator in the measurement data device sends (1+17.5+12.05+98.7+8.25+6.45). I've tried to understand the library code (.cpp and .h), but had no luck with solving this problem. Any thoughts on how this could be fixed?

Arduino code:

#define DATALINE_PIN 2
#define INVERTED 1
#define MAX_TIMEOUT 1000
//see:   http://arduino.cc/en/Reference/attachInterrupt
//for pins that support interupts (2 or 3 typically)


SDISerial connection(DATALINE_PIN, INVERTED);
char b_in[125];
char output_buffer[255];
char tmp_buffer[10];


void wait_for_message(char* buffer,char terminal){
   Serial.println("Waiting For input...");
   int i=0;
   while( true){
     if(!Serial.available())delay(500);
     else{
        buffer[i] = Serial.read();
        if(buffer[i] == terminal){
          buffer[i+1] = '\0';
          return;
        }
        i+=(buffer[i] >= 32 && buffer[i] <= 127);
     } 
   }
   
}

void setup(){
   Serial.begin(9600);
   connection.begin();
   delay(1000);
   Serial.println("Initialization Complete");
   
}
void loop(){

   wait_for_message(b_in,'!');
   sprintf(output_buffer,"[out]:%s",b_in?b_in:"No Output");
   
   Serial.println(output_buffer);
   
   char *response =connection.sdi_query(b_in,MAX_TIMEOUT);
   
   //sprintf(output_buffer,"[in]:%s",response?response:"No Response");
   Serial.println(response);
   Serial.flush();
   delay(1000);
   
}