Optimized code stops working

Question

On the following code I have a packet of 6 bytes that I write to a buffer. I pass the buffer as read_packet function argument. When optimized, the code doesn't work. I only got noise on the UART and even with the debugger I coudn't see the correct values. After some hours of trial and error I decided to select the level 0 of optimization and it started working. 
 What is the compiler doing? 
 while (true)
{
 uint32_t received[6];
 
 //received
 read_packet(received);
 //nrf_gpio_pin_toggle(led1);
 //nrf_gpio_pin_toggle(led3);
 app_uart_put(received[1]);
 //app_uart_put(12);
 
 //printf("The contents of the package is %u
", (unsigned int)received);
}

bool read_packet(uint32_t *buffer)
{
 //uint32_t *result = malloc(sizeof(uint32_t)*6);
 static uint32_t result[6];

 NRF_RADIO->EVENTS_READY = 0U;
 // Enable radio and wait for ready
 NRF_RADIO->TASKS_RXEN = 1U;

 while (NRF_RADIO->EVENTS_READY == 0U)
 {
 // wait
 }
 NRF_RADIO->EVENTS_END = 0U;
 // Start listening and wait for address received event
 NRF_RADIO->TASKS_START = 1U;

 // Wait for end of packet or buttons state changed
 while (NRF_RADIO->EVENTS_END == 0U)
 {
 // wait
 }

 if (NRF_RADIO->CRCSTATUS == 1U)
 {
 buffer[0] = packet[0];
 buffer[1] = packet[1];
 buffer[2] = packet[2];
 buffer[3] = packet[3];
 buffer[4] = packet[4];
 buffer[5] = packet[5];
 }
 NRF_RADIO->EVENTS_DISABLED = 0U;
 // Disable radio
 NRF_RADIO->TASKS_DISABLE = 1U;

 while (NRF_RADIO->EVENTS_DISABLED == 0U)
 {
 // wait
 }
 return 1;
}