Pipeline cache bursting generates multiple js files in template

[ableade]

Currently using pipeline in a production environment and having the following issues. After collectstatic is run with every new deployment and with PIPELINE_ENABLED set to true, using pipeline to output js files in the templates generates two different source files; one file with an appended hash and the original file without the hash.

<script type="text/javascript" src="/static/board1/js/a.js" charset="utf-8"></script>
<script type="text/javascript" src="/static/board1/js/widget/a.b74627162e09.js" charset="utf-8"></script>
<script type="text/javascript" src="/static/board1/js/widget/b.js" charset="utf-8"></script>
<script type="text/javascript" src="/static/board1/js/widget/b.c74627162e09.js" charset="utf-8"></script>

Both files exist in the static root folder but shouldn't cached storage produce the url for the latest version only. I have noticed that the duplicated files are ones not specified explicitly in the javascript section of the pipeline dict but are collected using directory wildcards e.g 'js/vendor/*.js'

Is there an explanation for this behaviour?