Unload is broken when a column contains certain characters

We are using the UNLOAD command to dump data to S3 in a TSV format and then read it using some other programs. Our UNLOAD command looks like the following:

UNLOAD ('SELECT column1, column2, column2 FROM some_table')
TO 's3://bucket/and/a/prefix/'
CREDENTIALS 'aws_access_key_id=<put_access_key_id_here>;aws_secret_access_key=<put_secret_access_key_here>'
ALLOWOVERWRITE
NULL AS '$$NULL$$'
ESCAPE
ADDQUOTES
DELIMITER '\t';

This works fine, but we noticed it breaks the output format when column1 contains the following string: "1% G".

Just to be clear:
column1 = "some text 1% General more text"
column2 = 10
column3 = "whatever"

We would expect to get a TSV with that looks like the following:
"some text 1% General more text"\t"10"\t"whatever"

Instead, we get:
"some text 1-NANeneral more text\t"10"\t"whatever"

Please note:

1. The TSV we get is broken - the first column isn't enclosed in quotes.
2. 1% G has been turned into 1-NAN.