Races on ref .lock files?

Hi all,

We're occasionally seeing a lot of 

  error: cannot lock ref 'stash-refs/pull-requests/18978/to': Unable to create '/opt/apps/..../repositories/68/stash-refs/pull-requests/18978/to.lock': File exists.

from the server side with fetches as well as pushes. (Bitbucket server.)

What I find strange is that neither the fetches nor the pushes even touch these refs (but the bitbucket triggers underneath might).

But my question is whether there are race conditions that can cause such messages in regular operation - they continue with 'If no other git process is currently running, this probably means a git process crashed in this repository earlier.' which indicates some level of anticipation.

- Andreas