digital communications - GNU Radio | Transceiver loopback adapted | Transmission stops unexpectedly

(This is a follow up question to a previous question: link)

I have implemented a flowgraph of a transceiver loopback inspired by the examples found at gnuradio/gr-digital/examples/packet, with a slight change - instead of driving the Packet_tx with:

• Message Strobe > Random PDU Generator > Packet_tx

I am using:

• File Source (/tmp/in_strings.txt) > Throttle > Stream to Tagged Stream > Tagged Stream to PDU > Packet_tx.

Then the data is recovered by the Packet_rx with:

• PDU to Tagged Stream > File Sink (/tmp/out_strings.txt)

Flowgraph below:

My expectation: I was hoping to transmit most of the data from in_strings.txt to out_strings.txt

What really happened:

• Chunks of data are lost during transmission in an intermittent fashion. Diff below:

• Transmission stops unexpectedly after ~40kB.

The files involved in this experiment:

I wonder what may be the cause of this?
Thanks in advance!