USRP might be broken but i don't know how to check

I have been transmitting random data using benchmark_tx and
benchmark_rx.
two things happen

  1. the first transmission will be successful. If i stop the command and
    retry it immediately nothing happens. I have to unplug and plug the ursp
    back again and it works. Any ideas as to why that happens and how do i
    fix
    it.
  2. If we look at the lines showing how the transmission went where we
    can
    see

ok=true pktno=116 n_rcvd 59 n_right 59

Can some one give me details as to what this is showing me. When I try
the
transmission a second or third time with the exact same configuration
the
ok=false jumps up dramatically and the n_right fallls dramatically. Any
particular reason? I have tried different things to fix it including
changing the distance between the radios but it doesn’t work.

Any ideas as to what is going on?
You help is much appreciated