Just avoid Cassanovum, they're awful. They almost always give really noticeable evaps, they always have a line there anyway and they are prone for false positives!
One Step are usually more reliable, however I'm pretty sure I have a wonky batch because the Lloyds tests I'm using are progressing daily atm but nothing on the ICs which is unusual as I usually see lines on those first. Lloyds btw are only about £6 for 2 and are buy one get one free