can anyone spot why this works fine in a customer saved search:

REPLACE(NS_CONCAT({pricinggroup} || ': ' || LTRIM({grouppricinglevel},'Base - 0')), ',', '  /  ')

however this does not?

CASE WHEN {pricinggroup} IS NULL then 'None' ELSE REPLACE(NS_CONCAT({pricinggroup} || ': ' || LTRIM({grouppricinglevel},'Base - 0')), ',', '  /  ') END