You can use console.log to print the arguments to your function. That way, you can find out what the input was when your function failed.
My guess is that your program thinks 1 is a prime.

Hey there. My unsubmitted solution works for every test except a single (1/111) random one. The test expects false, but instead gets a true. It happens every time I attempt to submit.

If there's some edge case I'm missing, what might that be?