Strange Problem with BBB(debian image) + UART4 + 4Dsystem 7lcd cape

Hi!
I hope someone can help my with BBB UART4 serial, I need to read data from Parallax RFID reader, strangest about this is it works some time especially ehen I plugin/ plugout pin connection multiple times. And RFID is connected to 4Dsystem 7lcd cape pin P9_11. Do I need use different pinMux for cape? or enable, define pin ?

I use Linux beaglebone 3.8.13-bone70 #1 SMP Fri Jan 23 02:15:42 UTC 2015 armv7l GNU/Linux

When I list ttyo’s ls -l /dev/ttyO* I get back crw-rw---- 1 root dialout 249, 4 Jan 1 01:18 /dev/ttyO4

I enable UART4 with jacascript wit cloud9 script

var RFIDPin = “P9_11”,
enableRFIDPin = “P8_19”,
RFIDport = ‘/dev/ttyO4’,
options = {
baudrate: 2400
//dataBits: 8,
//parity: ‘none’,
//stopBits: 1,
//buffersize: 1,
//flowControl: true
};

b.pinMode(enableRFIDPin, ‘out’);
b.digitalWrite(enableRFIDPin, enableRFIDstate);

b.serialOpen(RFIDport, options, onSerial);

function onSerial(x) {
setTimeout(function() {
if (x.err) {
console.log('ERROR ’ + JSON.stringify(x));
}
if (x.event == ‘open’) {
console.log(‘OPENED’);
}

if (x.event == ‘data’) {
processTags(x.data);
}
},500);
return true;
}

function processTags(symbolByte) {
var char = String(symbolByte);
console.log(char);
var charCode = parseInt(char.charCodeAt(0));

if(charCode === 10 && lastCharCode === 13)
allow = true;

if(allow) {
if(compareTag.length < 11) {
compareTag += char;
} else {
allow = false;
compareTags();
}
}

lastCharCode = charCode;

return true;
}

Can someone suggest some practices or advice, commands, books to fpund out what can cause thies issue?

Thanks,
Ingus