imapd: Error reading ACLs for INBOX..Junk: Invalid argument

[playalistic]

I'm getting lots of these showing up in the logs:

Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument
Dec 1 13:44:25 cmg-nix01 imapd: Error reading ACLs for INBOX..Junk: Invalid argument

I'm pretty certain this started since I added a filter to move SPAM into the .Junk folder. I since removed the filter and restarted the necessary services but it is still appearing in the mail.log.

I've also deleted the folder through the webmail client (Roundcube) which I installed separately and recreated it but no dice.

Can anyone help please?!