Capacitive Sensor gets stuck

Hello everyone,
I want to use CapacitiveSensor library in order to make my own aluminum keys piano. I have seen many videos online showing projects like the one I'm trying to do, but for some reason mine doesn't work.

Here's my cuircit:

Here's my code:

#include <CapacitiveSensor.h>

CapacitiveSensor   cs_7_6 = CapacitiveSensor(7,6);        // 10M resistor between pins 4 & 2, pin 2 is sensor pin, add a wire and or foil if desired

void setup()                    
{
   //cs_7_6.set_CS_AutocaL_Millis(0xFFFFFFFF);     // turn off autocalibrate on channel 1 - just as an example
   Serial.begin(9600);
}

void loop()                    
{
    long start = millis();
    long total1 =  cs_7_6.capacitiveSensor(5);

    Serial.print(millis() - start);        // check on performance in milliseconds
    Serial.print("\t");                    // tab character for debug windown spacing

    Serial.print(total1);                  // print sensor output 1
    Serial.println("\t");

    delay(10);                             // arbitrary delay to limit data to serial port 
}

This happens whenever I touch the aluminum foil:

First nothing happens (for ~1 sec), then it prints -2 as the capacity value, and when I release my finger from the foil it prints a very high value.

Anyone knows the reason for it? I'm searching for an answer for a long time and still can't find a solution...

Thanks!
Dan