### Please describe the problem.

I’ve just experienced something strange. When files are copied (instead of moved) into a repo with an assistant running, some of them get lost.

### What steps will reproduce the problem?

1. Start the assistant.
2. `cp -rv some-big-directory your-annex-repo/`
3. Wait for sync to finish.
4. Compare some-big-directory with your-annex-repo/some-big-directory.

It might be of some importance that I’m syncing this repo to 5 different machines.

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

git-annex version: 6.20170520
local repository version: 6
operating system: linux x86_64

### Please provide any additional information below.

Hard to tell, sometimes it happens, sometimes not.

### 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)

Sure, very cool, but this data loss thing creeped me out!
