How do I resolve garbled communications received by an XTEND-PKG-U

We have one XTEND-PKG-R (the remote) and one XTEND-PKG-U (the local) configured as point-to-point. For testing purposes, they are 20 feet apart. All messages are ASCII plain text.

Sometimes the transmission works (I receive the expected data at the local from the remote). But after a few minutes, the messages become garbled (a non-ASCII character repeated over and over). Power cycling the local (XTEND-PKG-U) does not resolve the issue.

The XTEND-PKG-R transmits streaming data and receives the occasional command. It is configured with the following settings (all other settings are default):
BD 6, RR0, MT 0, DT A2, MY A1

The XTEND-PKG-U receives streaming data and sends the occasional command. It is configured with the following settings (all other settings are default):
BD 6, RRA, MT 0, DT A1, MY A2

What is causing this issue and how can I resolve it?

Set the PL command on both to a value of 0.

I tried that but am still seeing the exact same issue.

What happens if you use a lower baud rate?