Taxonomy ID Filter only returns values relating to first incoming item within a Vocabulary

Hi, I have an issue when relating nodes using taxonomy. I have a list of products and have created a Vocabulary called 'RELATED PRODUCTS' which I use to link products to each other. When creating a product you are allowed to choose multiple values from the 'RELATED PRODUCTS' Taxonomy. I am then using pages / panels to create the page and trigger the view to return a list of the related product pages (using the 'RELATED PRODUCTS' taxonomy).

The Problem - I pass the View the 'RELATED PRODUCTS' Taxonomy ID for the current node but unfortunately the results only show items related to the first Taxonomy term selected in the 'RELATED PRODUCTS' list. What I want it to do is return items related to any of the selected terms in the 'RELATED PRODUCTS' taxonomy.

For example:

'RELATED PRODUCTS' Taxonomy includes terms 1, 2, 3, 4, 5
Product A has item 2 and 4 selected.
Related info A has item 4 selected
The view should return item 4 from Related info A when Product A is chosen but at the moment will only work if it relates to the first item selected for Product A.

From the example above, the view is a content pane receiving a taxonomy term ID from the panel (specified by setting term ID under the Argument input). I have tried setting allow multiple values under the Taxonomy contextual filter but it just doesn't appear to work. Of course it may just as well be that I haven't got my panel configured correctly to send multiple taxonomy Values but I assume this happens by default.

Clearly I am either missing something or using things the wrong way.

All help is greatly appreciated.