[Discuss-gnuradio] OFDM TX original example - output broken

[Sebastian Peters]

Hey All!

I'm fighting a problem with the original GNU Radio OFDM TX example from
https://github.com/gnuradio/gnuradio/blob/master/gr-digital/examples/ofdm/tx_ofdm.grc

Nothing is changed, except adding two File Sinks writing the data to two 
text files.
One File Sink is added at the random source and one at the OFDM Receiver 
output (parallel to Tag Debug).

Letting it run for a short while, gives me two output files: send.txt 
and received.txt
Then, I'm comparing the outputs in hex:
hexdump -C send.txt > send.txt.hex
hexdump -C received.txt > received.txt.hex
meld send.txt.hex received.txt.hex

(meld is a nicer diff tool)

Every time I do this, the received file is broken at some point. Six 
lines in hexdump (i.e. 6*16=96 bytes) are missing.
It occurs at random places, sometimes multiple times, and as the pattern 
is repeating but not always broken at the same point, you can see that 
it is not a special magic string that is causing it.
My expectation is an error-free transmission.

Can someone explain this behaviour? Am I missing some basic aspect?
I have noticed, that the packet length is 96bytes.

Sebastian