Intermittent exceptions when creating a new business process

Description of problem:
When creating a new business process, using the Designer, sometimes you get these in the server log:
ERROR [stderr] org.uberfire.java.nio.IOException: java.lang.RuntimeException: org.eclipse.jgit.api.errors.ConcurrentRefUpdateException: Could not lock HEAD. RefUpdate return code was: LOCK_FAILURE
ERROR [stderr] at org.uberfire.java.nio.fs.jgit.JGitFileSystemProvider.createDirectory(JGitFileSystemProvider.java:892)
ERROR [stderr] at org.jbpm.designer.repository.vfs.VFSRepository.createIfNotExists(VFSRepository.java:523)
ERROR [stderr] at org.jbpm.designer.repository.vfs.VFSRepository.createAsset(VFSRepository.java:341)
...

Followed by:
ERROR [org.jbpm.designer.web.preprocessing.impl.JbpmPreprocessingUnit] java.lang.RuntimeException: org.eclipse.jgit.api.errors.ConcurrentRefUpdateException: Could not lock HEAD. RefUpdate return code was: LOCK_FAILURE
ERROR [org.jbpm.designer.web.preprocessing.impl.JbpmPreprocessingUnit] java.lang.RuntimeException: java.lang.RuntimeException: java.io.IOException: Creating directory /home/zkrejcov/.niogit/repository1.git/objects/d7 failed
ERROR [org.jbpm.designer.web.preprocessing.impl.JbpmPreprocessingUnit] java.io.IOException: Creating directory /home/zkrejcov/.niogit/repository1.git/objects/0a failed
and similar. The process is created anyway.

Version-Release number of selected component (if applicable):
BPMS 6.0 CR1