Hi,
we’re tracking a reasonably severe bug in 13.7 that will manifest itself if your cookbooks rely on manipulating hashes or arrays of attributes. https://github.com/chef/chef/issues/6792 is the tracking issue. Once we’ve got a solution we’ll be making a point release of 13.7 to fix this.
We apologise for the inconvenience, and will be holding a public post-mortem once the issue is resolved.
-Thom