Unstable Plone.namedfile tests?

I have done some work on plone.scale to get rid of ConflictErrors revealed by plone.app.imagecropping.

I have requested various Jenkins jobs with that new code.
http://jenkins.plone.org/job/pull-request-5.0/586
...
http://jenkins.plone.org/job/pull-request-5.0/590

http://jenkins.plone.org/job/pull-request-4.3/168
...
http://jenkins.plone.org/job/pull-request-4.3/173

I get broken tests in plone.namedfile.

If I run plone.namedfile tests manually in buildout.coredev on my machine, I get from 0 to 3 failures, depending on the run.

It looks like a race condition issue. Has someone already seen issues with plone.namedfile tests ?

may you please create a bug report at either Products.CMFPlone or at plone.namedfile on github and mention the @plone/testing-team to get help here?

I debugged those tests. They were running too quickly for the granularity of modified.