QSerialPort: Syscall param ioctl(request) contains uninitialised byte, can't read from serial port

Hello everyone and thanks in advance,

I am able to find the port I want with QSerialPortInfo::availablePorts(),
let's call it "myport" then I pass it on to:

m_uart = new QSerialPort();
m_uart->setPort(myport);

I configure some stuff

m_uart->setDataBits(QSerialPort::Data8);
m_uart->setBaudRate(921600);
m_uart->setStopBits(QSerialPort::OneStop);

(I have tried setting the baud rate both before and after opening the device)

Then I open it while testing
if (m_uart->open(QIODevice::ReadWrite))

I get no error whatsoever.
However, I am unable to read any data from the serial port with this 5.3.0 version, while the 5.2.1-4 works perfectly, as well as other previous versions have been working for several months now.
The device blinks LEDs when I try to communicate which tells me it is receiving the data, but I am unable to read its output.

I have tested the device separately and am sure it is working properly. As I mentioned before, simply downgrading makes the issue go away.

The device is an FTDI chip, I have the following udev rule
SUBSYSTEM=="usb", ATTR

=="0403", ATTR

=="6001", GROUP="adm", MODE="0666"

Moreover, when I run the program, valgrind gives me the following output:
==6727== Syscall param ioctl(request) contains uninitialised byte(s)
==6727== at 0x6FA7E47: ioctl (in /usr/lib/libc-2.19.so)
==6727== by 0x568DB71: ??? (in /usr/lib/libQt5SerialPort.so.5.3.0)
==6727== by 0x568C3D1: QSerialPort::open(QFlags<QIODevice::OpenModeFlag>) (in /usr/lib/libQt5SerialPort.so.5.3.0)

which does not show with 5.2.1

Please let me know if there is any info missing, if so my apologies.