DQPSK Modeluation&Demodulation Problem

Was trying to do DQPSK but when I was demodulating, everything looks good except the "01" input. My code will output "10" for both "01" & "10" input.

Thank you! Following is my code.

bit_transmit=round(rand(10,1));

qpsk_transmission=1+1j;

for bit_index1=1:2:length(bit_transmit)
    bit_index2 = bit_index1+1;
    if bit_transmit(bit_index1) == 1 && bit_transmit(bit_index2)==1
        new_symbol = qpsk_transmission(end)*exp(1j*pi); %11
    end
    if  bit_transmit(bit_index1) == 0 && bit_transmit(bit_index2)==1
        new_symbol = qpsk_transmission(end) * (-1j); %01
    end
     if bit_transmit(bit_index1) == 0 && bit_transmit(bit_index2)==0
         new_symbol = qpsk_transmission(end) ; %00
     end
     if bit_transmit(bit_index1) == 1 && bit_transmit(bit_index2)==0
         new_symbol = qpsk_transmission(end) * (1j); %10
      end     
    qpsk_transmission=[qpsk_transmission, new_symbol];
    end

qpsk_received = qpsk_transmission*exp(1j*rand()*2*pi);

ref = qpsk_received(1);
bit_received=[];
for symbol_index=2:length(qpsk_received)
    cur = qpsk_received(symbol_index);
    angle_diff = angle(cur/ref);
    if abs(angle_diff) < pi/4 
        bitI = 0;
        bitQ = 0;
    else if  abs(angle_diff) < 3*pi/4
         bitI =1;
         bitQ = 0;
    else if abs(angle_diff) < 5*pi/4
        bitI = 1;
        bitQ = 1;
   else if abs(angle_diff)<7*pi /4
         bitI = 0;
         bitQ = 1;
        end
        end
        end
    end
    bit=[bitI bitQ];
    bit_received=[bit_received,bit];
    %
    ref = qpsk_received(symbol_index);
end

bit_transmit'
qpsk_transmission
qpsk_received
bit_received