They say to be 100% honest in your answers but there must be something else to it. If not then presumably I'd fail the personality questionnaire every time I took it.
To be blunt, yes. I'm sorry that you didn't succeed, but there'd be no point in a personality testing stage if it wasn't consistent.
but I'm completely lost as to what I should do about this questionnaire
.
I'm afraid there's not much you can do. If you retake it, and put down what you think we want to see, then you will get found out.