When compiling PDF, relative paths no longer work (Ubuntu serverguide)

Hi,

I tried asking for help on your IRC channel, and got no reply, so trying here.

Using a Ubuntu 16.04 server, I am attempting to compile the preliminary Ubuntu 16.04 Server guide, for preliminary publication on
help.ubuntu.com.
The build is failing to find the included png image files, used to indicate an inset  "Note" or "Warning" or whatever, and the
resulting PDF file is missing these icon indicators.
Note that these icons inclusions are not something new, and has always worked in the past. i.e. compiling with a 14.04 server.
I can get the compile to work properly by changing from relative to absolute paths in the file that defines this stuff, however that
is not a practical long term solution. 

I think, but am not sure, the problem is in the docbook.xsl package.

I am looking for help to identify the root issue and push for a solution or to come up with a viable workaround solution.

References:
https://bugs.launchpad.net/serverguide/+bug/1559783

Versions of docbook related stuff:
docbook        4.5-5.1ubuntu1    standard SGML representation system for technical documents
docbook-dsssl  1.79-9      modular DocBook DSSSL stylesheets, for print and HTML
docbook-utils    0.6.14-3ubuntu1    Convert DocBook files to other formats (HTML, RTF, PS, man, PDF)
docbook-xml    4.5-7.3  standard XML documentation system for software and systems
docbook-xsl      1.79.1+dfsg-1   stylesheets for processing DocBook XML to various output formats

Doug Smythies