CCS/TMS320F28377S: SCI RS485 problem

I am trying to implement the modbus protocol.

After many attempts and help from the forum, I finally manage to correctly receive the frames but I have another problem. 
When I pick up the frame in the interrupt, then I have to switch rs485 to sending mode (I do it using GPIO19 connected to DE RS485). 
When I do these operations, I get error flags like FE and PE. Does anyone have an idea what could be wrong? 

I put my code

Best regards
Szymon

interrupt void scicRxFifoIsr(void)
{
    Uint16i = 0;
    Uint16 z = 0;
    while(ScicRegs.SCIFFRX.bit.RXFFST != 0){
        RxMODBUS[i]=ScicRegs.SCIRXBUF.all;
        i++;// Read data}
   for(z=0;z<500;z++){
    }
    }

    GpioDataRegs.GPASET.bit.GPIO19 = 1;

    ScicRegs.SCIFFRX.bit.RXFFOVRCLR=1;   // Clear Overflow flag
    ScicRegs.SCIFFRX.bit.RXFFINTCLR=1;   // Clear Interrupt flag

    PieCtrlRegs.PIEACK.all|=0x80;       // Issue PIE ack
}

void scia_fifo_init()
{
   ScicRegs.SCICCR.all = 0x0067;      // 1 stop bit,  No loopback
                                      // No parity,8 char bits,
                                      // async mode, idle-line protocol
   ScicRegs.SCICTL1.all = 0x0003;     // enable TX, RX, internal SCICLK,
                                      // Disable RX ERR, SLEEP, TXWAKE
   ScicRegs.SCICTL2.bit.TXINTENA = 0;
   ScicRegs.SCICTL2.bit.RXBKINTENA = 1;
   ScicRegs.SCIHBAUD.all = 0x0000;
   ScicRegs.SCILBAUD.all = 0x00A2;
   ScicRegs.SCICCR.bit.LOOPBKENA = 0; // Enable loop back
   ScicRegs.SCIFFTX.all = 0xC021;
   ScicRegs.SCIFFRX.all = 0x0028;
   ScicRegs.SCIFFCT.all = 0x00;

   ScicRegs.SCICTL1.all = 0x0023;     // Relinquish SCI from Reset
   ScicRegs.SCIFFTX.bit.TXFIFORESET = 1;
   ScicRegs.SCIFFRX.bit.RXFIFORESET = 1;
}