No estoy seguro de lo que está tratando de hacer, pero tiene dos cláusulas de selección. Haz esto en su lugar:
SELECT *
FROM ( SELECT *
FROM orders_products
INNER JOIN orders ON orders_products.orders_id = orders.orders_id
WHERE products_id = 181) AS A
JOIN ( SELECT *
FROM orders_products
INNER JOIN orders ON orders_products.orders_id = orders.orders_id
WHERE products_id = 180) AS B
ON A.orders_id=B.orders_id
Actualización:
Probablemente podrías reducirlo a algo como esto:
SELECT o.orders_id,
op1.products_id,
op1.quantity,
op2.products_id,
op2.quantity
FROM orders o
INNER JOIN orders_products op1 on o.orders_id = op1.orders_id
INNER JOIN orders_products op2 on o.orders_id = op2.orders_id
WHERE op1.products_id = 180
AND op2.products_id = 181
