{{layout area="frontend" handle="sales_email_order_invoice_items" invoice=$invoice order=$order}}
The above block/layout handle in my transactional email is using the base theme when the invoice is created - however strangely when the invoice is resent, it uses the correct theme. Both actions are being carried out in the admin.
I've tried:
{{layout area="frontend" package="foo" theme="bar" handle="sales_email_order_invoice_items" invoice=$invoice order=$order}}
but have had no luck.