Client raising an exception with a message of 'Unknown input found while converting a hex value'

This was seen crashing ndscope.

A series of manipulations can be made which case the application crash (or request to fail) with the following error:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/ndscope/nds.py", line 267, in run
    bufs = fetch(self.channels, self.start_end)
  File "/usr/lib/python3/dist-packages/ndscope/nds.py", line 193, in fetch
    return conn.fetch(*args)
  File "/usr/lib/python3/dist-packages/nds2.py", line 3426, in fetch
    return _nds2.connection_fetch(self, gps_start, gps_stop, channel_names)
TypeError: Unknown input found while converting a hex value

This points into the NDS2 client. Upon digging, this is an exception thrown in client/src/common/nds1/common/basic_io.hh in the basic_io::from_hex_nibble(int nibble).

More debugging is needed to track down a minimal crashing error.