OTA Encoding/Decoding with Ettus SDR & GNURadio

Hi, I am trying to do over-the-air (OTA) encoding and decoding using GNURadio and an Ettus SDR. I used a basic flowgraph (shown at https://imgur.com/a/P846OSe) which I know can correctly decode the encoded signal w/ 0 BER in simulation (w/o/ the SDR blocks). However, using the SDR sink/source blocks, I can no longer recover the correct bits. Here is how the visualized recovered data looks like: https://imgur.com/a/Z5JfvjS. As you can see I am unable to recover the original encoded bits. 

So my questions are:

1) What am I doing wrong?

2) Are there any articles/tutorials which discuss how to encode/decode w/ GNURadio & Ettus SDR?

Thanks,

Roman