My experience is that some developers can write code but most memorize patterns and follow trends. If your questions require some solution different from a memorized pattern they will fail.

Another way to approach this: can the candidate communicate? If they cannot write original code odds are they probably cannot clearly write steps of simple instructions explaining a problem or solution as they do not have experience thinking through the problem without a lot of help.

Most places I interviewed at last year claimed to be looking for senior developers but in practice were only looking for trend chasers doing things in a very limited way that appeals primarily to beginners memorizing patterns.