Yeah there's something going on with the UART configuration of this Betz board which causes the chip to reset itself at random points during serial communications.

Whenever I issue a large series of commands to the thing all at once, it almost always resets itself, meaning that most of the commands don't get through at all.

On rare occasions it resets itself even if I type a fairly short innocuous command in the serial debug terminal, for example:

SET CONTROL BATTERY 0 0 0 0
WRAP THOR AI (6.2.0 build 1122)
Copyright (c) 2003-2017 Silicon Labs Inc.
READY.

I can't simply "delay" my commands to the thing because some of the stuff will need to be very fast responses.

None of this happened with the BlueGiga development board, I could send commands as fast as I wanted and there was no problem.

My first try was to disable the feature that puts it in and out of data mode via DTR signaling:
SET CONTROL ESCAPE - 00 0

That didn't help. Looking at other stuff.