FreeRTOS with configUSE_TICKLESS_IDLE activated causes a bad behaviour in the RX of UARTE

Question

Hi to everybody, 
 I am working with nrf52 and SDK11. In my project I am using freertos and an UARTE with this configuration: 
 
 9600bps 
 TX/RX (no CTS; no RTS) 
 HW flow control disabled. 
 No parity. 
 DMA. 
 
 DMA TX buffer of 16 bytes. 
 DMA RX buffer of 16 bytes, double buffer of 8 bytes. 
 If the configUSE_TICKLESS_IDLE is set the UARTE reception behaves strangely. I am sending frames of 7 bytes [11 22 33 44 55 66 77] looking at my uart handler once I receive NRF_DRV_UART_EVT_RX_DONE event instead of having those 7 bytes in the first 8 bytes buffer the result I get is: 
 DMA RX buffer 1: 11 22 33 44 55 66 00 00 
 DMA RX buffer 2: 77 00 00 00 00 00 00 00 
 And the 'p_event->data.rxtx.bytes' has a value of 6. So it seems the 7 bytes has been received but I dont know why there are only 6 registered and the 7th is in the second part of the DMA RX buffer. 
 I have a gpiote related to the RX_PIN (rising edge) to control the RX timeout (suposed to end a reception after 20ms of RX_PIN inactivity). This way I can avoid waitting for a complete DMA buffer size reception. 
 I have verified that the 7 bytes of my test frame are reaching the nrf52 in a raw. From the gpiote event handler I am reseting the timer with "xTimerResetFromISR". And once the timer expires in the timer handler I abort the uart rx: 
 /* Abort the current UARTE RX */
CRITICAL_REGION_ENTER();
nrf_drv_uart_rx_abort();
CRITICAL_REGION_EXIT(); 
 
 Actually I am using the external/freertos files from the SDK12 that are supposed to fix some bugs the SDK11 has. I have also tried to solve the issue with the recomendations written in this other thread 
 But with the "port_cmsis_systick.c" attached by Aryan the issue is not fixed. With this file and using the updateRTOSTick() call in the handlers that use any API call to FreeRtos I am no able to receive anything, the program gets blocked at vPortSuppressTicksAndSleep. 
 Does anybody know why the UARTE is behaving this way and broking the frame and only capturing part of the info? 
 Thanks in advance for your help. 
 Nota: I cant post or attach my code so I is necessary I can create a support case and share it.