I am using **TeamCity** on ubuntu (`TeamCity Professional 9.1.7 (build 37573)`). And having some problems with automatic merges lately (git).
I haven't changed anything in the configuration from when it used to work.
I tried to remove the work directory. it only helped for a couple of merges.

**Symptoms:**
The build log looks clean, and I am getting this on the build overview:

```
Failed to merge sources in VCS root foo. Merge error 'git fetch'     command failed.
stderr: git@bitbucket.org:foo/foo.git: channel is not opened.
exit code: 1.

```

**Although**, in the agent running this i am getting a totally different error in `teamcity-vcs.log`:

```
[2016-03-30 15:14:31,722]   INFO -      jetbrains.buildServer.VCS - [/home/ubuntu/BuildAgent/work/7676127c0a691f42]: /usr/bin/git show-ref refs/remotes/origin/foo 
[2016-03-30 15:14:31,775]   INFO -      jetbrains.buildServer.VCS - [/home/ubuntu/BuildAgent/work/7676127c0a691f42]: /usr/bin/git log -n1 --pretty=format:%H%x20%s 193f46d88205c5e419a8a7458e742ce9b598cca8 
-- 
[2016-03-30 15:14:31,797]   WARN -      jetbrains.buildServer.VCS - '/usr/bin/git log -n1 --pretty=format:%H%x20%s 193f46d88205c5e419a8a7458e742ce9b598cca8 --' command failed.
stderr: fatal: bad object 193f46d88205c5e419a8a7458e742ce9b598cca8 
[2016-03-30 15:14:31,798]   INFO -      jetbrains.buildServer.VCS - [/home/ubuntu/BuildAgent/work/7676127c0a691f42]: /usr/bin/git fetch --progress origin +refs/heads/foo:refs/remotes/origin/foo 
[2016-03-30 15:14:35,832]   WARN -      jetbrains.buildServer.VCS - Error output produced by: /usr/bin/git fetch --progress origin +refs/heads/foo:refs/remotes/origin/foo 
[2016-03-30 15:14:35,832]   WARN -      jetbrains.buildServer.VCS - remote: Counting objects: 2, done.ESC[K
remote: Compressing objects:  50% (1/2)   ESC[K
remote: Compressing objects: 100% (2/2)   ESC[K
remote: Compressing objects: 100% (2/2), done.ESC[K
remote: Total 2 (delta 1), reused 0 (delta 0)ESC[K
From bitbucket.org:bar/bar
   62ba378..193f46d  foo  -> origin/foo 

```

As if the log command failed..

Thanks.

---

Update: I got an update that there is anecdotal evidence that this is due to changes specifically in BitBucket's git over SSH servers.