external data access crashing in cvmfs-2.3.1 when debug logging enabled

I'm seeing a segmentation violation signal 11 in cvmfs-2.3.1 when accessing an external file on a dCache WEBDAV door. The problem does not happen in cvmfs-2.3.0, or when using a stashcache server with 2.3.1. I will post a stacktrace in the comments.