Every retrieval a duplicate

Hi. 

Getmail is retrieving two copies of all emails in my Inbox. These 
are simultaneous retrievals from a single getmail command. 

It is also duplicating retrievals of many emails that have been moved 
from Inbox into custom folders; I can't see any pattern to when this 
happens and doesn't happen. 

I'm retrieving from a gmail IMAP account. 

My rc file is below. Any help will be much appreciated. 

# More configuration options here:
# http://pyropus.ca/software/getmail/configuration.html
[retriever]
type = SimpleIMAPSSLRetriever
server = imap.gmail.com
mailboxes = ("Inbox", "[Gmail]/All Mail") # optional - leave this line out to just grab inbox
username = redacted
password = redacted

[destination]
type = MDA_external
path = /usr/bin/procmail
arguments = ("-f", "%(sender)", "-m", "$HOME/.procmailrc")

[options]
verbose = 2
message_log = ~/.getmail/log
message_log_verbose = true
max_messages_per_session = 100

read_all = false

delivered_to = false
received = false