### Please describe the problem.

I am trying to verify that my files are where they should after having updated my remotes to use chunking. I do get the following two error messages, but then git-annex reports that everything is Ok. I find it slightly scary and thus wonder if the fsck command in all cases do a conservative enough check. All other files (except two other ones where it noticed that they where in fact not on the remote do not report any errors.)

When running the fsck command for all files I got the following slightly worring message for one file.

    fsck Ekonomi/2014-06-02_Elavräkning.pdf (checking box.com5...) (checking box.com5...) (checking box.com5...) 
    79%         23.2KB/s 26s
      Error_Packet "partial packet: expecting 16448 bytes, got: 891"
    ok
                      
Reading the message it seems that the file was not correctly downloaded, but still deemed Ok enough by git-annex. 

Further while writing this report I get the following message from a remote  using the external protocol:
 
    fsck Deklaration/archive/2012/DE/Steuerklärung Formular.pdf 
    93%        221.9KB/s 12s
      /Users/carlmod/Annex/.git/annex/tmp/GPGHMACSHA1--0e7e4951e2650ac636bc3fc17c673f1f2dfb3071: openBinaryFile: does not exist (No such file or directory)
    ok                      

Source code for this remote is not yet published online, as i would want to build it slightly more reliable before releasing it. It however passes the remote test suite without any problem. 
### What steps will reproduce the problem?

Not really sure, but rerunning the commands show that the openBinaryFile happens here for this particular file. 

### What version of git-annex are you using? On what operating system?

    $ git annex version
    git-annex version: 5.20141125
    build flags: Assistant Webapp Webapp-secure Pairing Testsuite S3 WebDAV FsEvents XMPP DNS Feeds Quvi TDFA CryptoHash
    key/value backends: SHA256E SHA1E SHA512E SHA224E SHA384E SKEIN256E SKEIN512E SHA256 SHA1 SHA512 SHA224 SHA384 SKEIN256 SKEIN512 WORM URL
    remote types: git gcrypt S3 bup directory rsync web webdav tahoe glacier ddar hook external

built using Homebrew (i.e. in a cabal sandbox) on OS X Yosemite 10.10.1

