The construction of the SQL query, aside from range limitations, has not changed since its original version. Did you have or notice this issue before?

I don't know how mySQL decides to order its results in the absence of specific "order by" commands... that needs someone with expert knowledge. Is there actually a definite order, or does it depend on some random access effects from efficient searching techniques? It might be possible to add an "order by products_id" clause in the right sequence so the overall results keep orders together. I would have to research the sequence of operation of multiple items in the "order by".

Are you wanting the CSV product output to match the invoice order? Does the invoice order match the db stored order, and does that match the order in which the customer actually added the products to the cart?