LBT + retries wiht CC1120 - Getting stuck in TxPacket (interrupt not firing)

Hi,

I'm using the CC1120 to send fixed size packets of 20 bytes. I have tried to incorporate listen-before-talk, as well as up to 3 random backoff time retries for each packet. After a few dozen broadcasts, the GPIO0 interrupt signal stays low and I am constantly timing out.

Is there anything else I need to re-arm before trying to resend a packet, or any suggestions as where I might be going wrong? I have pasted in my code below.

void TxPacketRf(uint8_t* data)
{
    uint8_t rssi;
    uint8_t txBuffer[PKTLEN+1] = {0};
    bool complete = false;
    uint8_t retries = 3;
    
    packetCounter++;
    
    trxRfSpiInterfaceInit();
    
    txBuffer[0] = PKTLEN;
    for(uint8_t i = 1; i < PKTLEN+1; i++)
    {
        txBuffer[i] = *data++;
    }
    
    while((complete == false)&&(retries--))
    {
        //Write packet to tx fifo
        cc112xSpiWriteTxFifo(txBuffer,sizeof(txBuffer));
        
        //Listen-Before_Talk block from here
        // Strobe RX
        trxSpiCmdStrobe(CC112X_SRX);
        
        // Wait for RSSI to be valid
        do
        {
            cc112xSpiReadReg(CC112X_RSSI0, &rssi, 1);
        } while (!(rssi & 0x01));
        
        // Air is free, strobe TX to send packet
        trxSpiCmdStrobe(CC112X_STX);
        
        //generate a 10ms (+up to 5ms random) timeout value
        uint8_t timeout = 0;
        sd_rand_application_vector_get((uint8_t *)&timeout, 1);
        timeout = timeout%6;        //to get 0-5
        timeout+=10;                        //15 milliseconds
        timeout*=10;                        //150 * 100us = 15ms

        while((packetSemaphore != ISR_ACTION_REQUIRED)&&(timeout > 0))
        {
            nrf_delay_us(100);
            timeout--;
        }
        packetSemaphore = ISR_IDLE;
        
        if(timeout > 0)
        {
            //packet went
            complete = true;
            printf("rfsent\n\r");
        }
        else
        {
            printf("timed out\n\r");
        }
    }
}

Thanks