Binary serial port reading messes up data sometimes - serial-port

Question

I have a serial port. The other program writes to the serial port in every 0.2 second. Each time, the data written to the serial port is always 83 bytes in length. The serial port can be read correctly using minicom.
I have a program that can read the serial port. Each time, the byte stream written to the serial port is:
65 66 67 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90
Most of the times the data can be received correctly. However, sometimes the data is messed up. Once the data is messed up, almost all the incoming messages are messed up.
Sometimes, I get output from my code as:
65 0 66 67 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 65 66 67
This is weird. Since apparently, there is a 0 after the first 65. Also, the last three bytes is 65 66 67, which looks like is the begging of a new message.
The code for opening and configurating the serial port is:
int serial_fd = open(device, O_RDWR | O_NOCTTY | O_NDELAY|O_NONBLOCK);
if (serial_fd < 0) {
return -1;
}
struct termios options;
tcgetattr(serial_fd, &options);
options.c_cflag |= (CLOCAL | CREAD);
//8N1 mode
options.c_cflag &= ~CSIZE;
options.c_cflag |= CS8;
options.c_cflag &= ~CSTOPB;
options.c_cflag &=~PARENB;
options.c_cflag &= ~CRTSCTS;
options.c_lflag &= ~(ICANON|ECHO|ECHONL|ISIG|IEXTEN);
options.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP|INLCR|IGNCR|ICRNL|IXON);
options.c_oflag &= ~OPOST;
cfsetospeed(&options, B115200);
cfsetispeed(&options, B115200);
tcsetattr(serial_fd, TCSANOW, &options);
tcflush(serial_fd, TCIFLUSH);
The code for reading from the serial port and printing out the received message is:
uint8_t *buff,buff_data[100];
buff = buff_data;
int len,fs_sel;
fd_set fs_read;
int expectedLength=83;
int len_acc = 0;
while(1){
FD_ZERO(&fs_read);
FD_SET(serial_fd, &fs_read);
fs_sel = select(serial_fd+1,&fs_read,NULL,NULL,NULL);
if(fs_sel)
{
len = read(serial_fd, buff, expectedLength-len_acc);
if (len<=0) continue;
len_acc += len;
if (len_acc < expectedLength) {
buff += len;
continue;
}
len_acc = 0;
buff = buff_data;
for (int i=0; i<expectedLength; i++){
std::cout <<(int)buff[i]<<" ";
}
std::cout<< std::endl;
}
}
Thanks for your help.