This commented line in the default function was the reason of the issue:
Code:
static double charToPan(unsigned char val)
{
double pos = ((double)val*1000.0 + 0.5) / 127.0;
pos = (pos - 500.0) / 500.0;
//if (fabs(pos) < 0.08) pos = 0.0;
return pos;
}