Look at the receiver output with a scope and see how much noise is present and whether you expect a UART to clock in the data properly. You see, it takes only something with the appearance of a start bit to get the UART started shifting in bits.

I have been informed that if I use bit-banging at the receiver instead of UART, would solve the problem. I don't know it is true or not.

And most likely bit-banging at the transmitter too. Bit-banging transmit and receive are done when internal peripheral subsystems in incapable of generating the waveform of the encoding scheme chosen to suit the RF link's characteristics.