Answering my own question I ran the xslt's in question the the xslt visualizer and get the following error:

System.Xml.Xsl.XslTransformException: Cannot find a script or an extension object associated with namespace 'urn:tagsLib'.
   at System.Xml.Xsl.Runtime.XmlQueryContext.InvokeXsltLateBoundFunction(String name, String namespaceUri, IList`1[] args)
   at (XmlQueryRuntime 
{urn:schemas-microsoft-com:xslt-debug}runtime, XPathNavigator 
{urn:schemas-microsoft-com:xslt-debug}current, XPathNavigator post)
   at (XmlQueryRuntime 
{urn:schemas-microsoft-com:xslt-debug}runtime)
   at Root(XmlQueryRuntime 
{urn:schemas-microsoft-com:xslt-debug}runtime)
   at Execute(XmlQueryRuntime 
{urn:schemas-microsoft-com:xslt-debug}runtime)
   at System.Xml.Xsl.XmlILCommand.Execute(Object defaultDocument, 
XmlResolver dataSources, XsltArgumentList argumentList, 
XmlSequenceWriter results)
   at System.Xml.Xsl.XmlILCommand.Execute(Object defaultDocument, 
XmlResolver dataSources, XsltArgumentList argumentList, XmlWriter 
writer)
   at System.Xml.Xsl.XslCompiledTransform.Transform(IXPathNavigable 
input, XsltArgumentList arguments, XmlWriter results, XmlResolver 
documentResolver)
   at System.Xml.Xsl.XslCompiledTransform.Transform(IXPathNavigable 
input, XsltArgumentList arguments, TextWriter results)
   at umbraco.macro.GetXsltTransformResult(XmlDocument macroXML, 
XslCompiledTransform xslt, Dictionary`2 parameters) in 
d:\TeamCity\buildAgent\work\75c63e4d2422667e\umbraco\presentation\macro.cs:line
 744
   at 
umbraco.presentation.umbraco.developer.Xslt.xsltVisualize.visualizeDo_Click(Object
 sender, EventArgs e) in 
d:\TeamCity\buildAgent\work\75c63e4d2422667e\umbraco\presentation\umbraco\developer\Xslt\xsltVisualize.aspx.cs:line
 69

something is wrong with my tagsLib? what to do to fix it?

What version of Umbraco is your problematic installation running?

/Jan

Didn't have the following in my config/xsltextensions.config

<XsltExtensions>
  <ext assembly="umbraco.editorControls" type="umbraco.editorControls.tags.library" alias="tagsLib">
  </ext>
  <ext assembly="Runway.Blog" type="Runway.Blog.BlogLibrary" alias="BlogLibrary">
  </ext>
  <ext assembly="Umbraco.Forms.Core" type="Umbraco.Forms.Library" alias="umbraco.contour">
  </ext>
</XsltExtensions>

all good now

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