### Please describe the problem.
In my repo network, multiple repos are cropping up with an "invalid object" error.  The object in question changes and appears to be from git-annex's hidden branch.

### What steps will reproduce the problem?
This is happening after I add a mess of new files and sync, within a couple times of doing this, after a day or so.

### What version of git-annex are you using? On what operating system?
6.20160518-g766728c on linux

### Please provide any additional information below.

[[!format sh """
# Example error, file in question will change
    (recording state in git...)
    error: invalid object 100644 d547f60ac6c53f8bf38999d93ce954e3dfca1656 for
    '051/0b4/SHA3_512-s12447441634--b84ff2ead694b9d355d8deb4eae620b5979f0127f127718d53d02cd32f1020fba45f1e63723484462beb10110328dab29d875ea1788f949ce541640603fa73c0.log'
    fatal: git-write-tree: error building trees
    git-annex: failed to read sha from git write-tree
# End of transcript or log.

# log of attempting to determine the issue yesterday
2016-05-22

Issue history:
Original annex started being unable to finish commit.
Second annex, I cloned and copied objects folder over.  Soon, same issue.
Third annex, cloned from elsewhere, use git annex get to get objects from
broken repo.  Same issue developed.
Fourth annex, cloned from elsewhere, was able to commit successfully
prior to adding objects from broken repo.
Some object in the broken repo seems to be causing this issue somehow.

Plan to resolve:
- copy all objects over again.  verify that issue immediately develops.
  
  I expect the issue will trigger when I add a set of objects with litelog.
  So I could narrow it either by narrowing the objects I add with litelog,
  or by narrowing the object I copy from the broken repo.

  I'll narrow the issue between the two, first.

annex: used to be annex.2, busted
annex.3: third repository, busted, holds objects
annex.4:
  1. cloned from delta
  2. added logs, no issue
  3. 10:24:24 EDT rsync --delete-during'd objects in from annex.3
  4. 10:25:10 EDT added small test file, sync'd with delta fine
  5. 2016-05-22 10:27:38
      I ran fetchall but ran by root by mistake.
      files were added with wrong permissions
      fixed permissions.  only two files were cpied, voicerecorder and muse.
      sync works fine.'
  6. ran fetchall (as root) again, got 4 sensorium files
  7. add and sync seems to work fine.
  So now this repository is functioning with additional objects copied into
  its annex folder.  It must have been something else which caused the issue
  on the other repo I initialized this way.
  8. I foolishly tried to git annex add the alphabetically first object from
  the annex/objects folder to get it annex's logs.  It failed when trying to
  _delete_ it to replace it with a link to itself, luckily it was not writable.

  I'll try using this repo - 2016-05-22 10:36:24 EDT

  I'll add the remotes one at a time and sync with them, adding litelog after
  each one.

  9. 2016-05-23 00:08 EDT
    Issue reoccurred uploading data from phone. Was a larger block of data.
    First fetched
    then added
    then copied to delta
    issue showed at end of copy to delta

    perhaps the issue resides on delta ??? but we synced to delta fine before
    the issue must happen over time while I am away from the computer
    or respond to a large amount of logs being uploaded
    or it could have happened as a result of my work on the nested repo
 10. 2016-05-23 00:10:15 EDT
   $ git annex copy --to=gitlab
   06:55 EDT
   $ git annex sync gitlab
    both commands ran without issue
    delta also fsck'd fine
 11. 2016-05-23 07:01 EDT
    local repo fsck'd fine
"""]]

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)
Very stable.  Still excited.