[Discuss-gnuradio] Firs byte always missing on TCP BPSK encoder

I have a BPSK modulator/demodulator simulator script (attached) that has
me a little perplexed. I have a TCP source on the input and a TCP sink
on the output. The Encoder is setup for a payload length of 1.

Everything works except that I seems to always lose the first byte.

What I do is run the script and then run:
nc localhost 60000 in one terminal
and nc localhost 60001 in another

If I type, "this is a test" in the first terminal (minus the quotes) and
hit enter, I see "his is a test" in the second terminal. So it looks
like things are working, but why would I be losing that first byte? It
seems to happen every time I start the script fresh.