having the following configuration:
views content pane:
a contextual filter: has taxonomy term id
override title: Related News for %1
Allow multiple values
validation with filter type: Term IDs separated by , or +
the views pane preview works for single and concatenated term id's as contextual filter argument.
what doesn't work is embedding the views pane sucessfully into a panel:
panel for node template
context: relationship "Multiple terms from node" for a specific vocabulary with option OR + as concatenator
content: passing the context to a views content pane as "Term ID of all term, separated by + or ,"
the argument seems not to get passed. it will when using "Term ID of first term" instead of "Term ID of all term, separated by + or ,"
this is related to the support request #1111384: How to create a panel with related content based on multiple terms.