[Dovecot] dsync-local(user): Error: proxy client timed out

[Metro Domain Admin]

Hello,

I have an intermittent but frequent problem using dsync backup. The
command outputs:

dsync-local(user): Error: proxy client timed out

Then dies with exit code 75. Any subsequent attempts to re-run the
backup invariably fail like this:

dsync-local(user): Warning: Destination mailbox INBOX has been modified,
need to recreate it before we can continue syncing
dsync-local(user): Error: read() from worker server failed: EOF
dsync-local(user): Error: msg-copy returned invalid input: 
dsync-local(user): Error: remote: dsync-remote(user at domain.com): Error:
Can't delete mailbox INBOX: INBOX can't be deleted.
dsync-remote(l_user at domain.com): Error: command MSG-SAVE failed
dsync-local(user): Warning: Mailbox changes caused a desync. You may
want to run dsync again.

The syntax I am using is:

dsync -u $user backup \
ssh -i <idfile> <user at host> \
dsync -u l_$user

We have this running in a script that loops through all users. The error
happens mostly on the larger mailboxes but I've seen it succeed on the
largest ones then fail on smaller. One mid-sized account now fails
consistently. 

The backup is running from a Mac OS PPC server running 2.1.12 The target
is a Linux Intel box running 2.1.13, but I had the same problem sending
to a Mac OS Intel on 2.1.12. Mdbox in all cases.

Thanks,
Tony