Problem with NRF SDK 5 compilation on Segger Embedded Studio

Question

So I've been playing around with some code example to make UART work (which I did eventually) using NRF SDK 5 (v17). However the last version of SES (8.22a) requires some tweaks in order to make it work. Like setting Library I/O setting to RTT (because otherwise stdout will throw errors) and also removing the limit of .rodata and .text sections (this is irrelevant I guess anyway). The code looks like this:

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include "app_uart.h"
#include "app_error.h"
#include "nrf_delay.h"
#include "nrf.h"
#include "bsp.h"
#include "nrf_uart.h"
#include "SEGGER_RTT.h"


#define RX_SIZE 256
#define TX_SIZE 256
#define UART_HWFC APP_UART_FLOW_CONTROL_DISABLED


// A simple error handler for uart if something goes wrong...
void uart_err_handle(app_uart_evt_t * p)
{
    printf("HERE: %d", p->evt_type);
}

int main(void)
{

    //printf("Board Loaded");
    bsp_board_init(BSP_INIT_LEDS);    // initialize leds
                                    //
    uint32_t err_code; // a variable to hold the error value

    const app_uart_comm_params_t com_params = // struct to hold the uart configurations
    {
        RX_PIN_NUMBER,
        TX_PIN_NUMBER,
        RTS_PIN_NUMBER,
        CTS_PIN_NUMBER,
        UART_HWFC, // hardware flow control disabled
        false, // parity = none
        NRF_UART_BAUDRATE_115200 // set this baud rate for communication
    };

    APP_UART_FIFO_INIT(&com_params, RX_SIZE, TX_SIZE, uart_err_handle, APP_IRQ_PRIORITY_LOWEST, err_code);
    APP_ERROR_CHECK(err_code);

    while(true)
    {
        uint8_t rx_ch;
	while (app_uart_get(&rx_ch) != NRF_SUCCESS);

	if (rx_ch == 't')
	{
	    bsp_board_leds_on();
	    printf("Leds Turned On!!\r\n");
	}
	else if (rx_ch == 'k')
	{
	    bsp_board_leds_off();
	    printf("Leds Turned Off!!\r\n");
	}
    }
}


/** @} */

As you can see it's just a basic example, but my question is this, IF I compile it with SES 5.42 (which I understand is the latest tested on v17) THEN everything works fine, but if I compile it with SES 8.22a (RTT option enabled) the function app_uart_get() never gets a result back... why is this ? and should I always use SES 5.42 ? are there any drawbacks ?