I have a query that is aimed at Transfer Orders, it is referencing Transaction and Transactionline tables, I need to filter by transactionlinetype, the result shows perfectly fine in the UI (in this case "RECEIVING") however when I add transactionlinetype = 'RECEIVING' into the where clause I get no results found, any ideas?

Have you done a query just for that internal ID & looked at what the actual transactionlinetype is? You might need to use BUILTIN.DF() or similar

Yep, it returns 3 different ones, one of them being RECEIVING