amazon-redshift-utils: Exception 'unpack_from' in ColumnEncoding only with some tables

I’ve just cloned from the master branch and am using the ColumnEncoding script through Docker by running

docker run --net host --rm -it --env-file scaling-test.env amazon-redshift-utils column-encoding

For some of the Redshift tables, I get the following error:

-- [6] [6] Running insert into public."example_table_$mig"  select * from public."example_table" order by timestamp;
Exception unpack_from requires a buffer of at least 5 bytes during analysis of example_table
Traceback (most recent call last):
  File "ColumnEncodingUtility/analyze-schema-compression.py", line 788, in analyze
    if not run_commands(get_pg_conn(), statements):
  File "ColumnEncodingUtility/analyze-schema-compression.py", line 383, in run_commands
    conn.rollback()
  File "/usr/local/lib/python2.7/site-packages/pg8000/core.py", line 1545, in rollback
    self.execute(self._cursor, "rollback", None)
  File "/usr/local/lib/python2.7/site-packages/pg8000/core.py", line 1741, in execute
    self.handle_messages(cursor)
  File "/usr/local/lib/python2.7/site-packages/pg8000/core.py", line 1875, in handle_messages
    code, data_len = ci_unpack(self._read(5))
error: unpack_from requires a buffer of at least 5 bytes

I haven’t identified any pattern among the tables that cause the issue.