Polyglot, I realised that your problem may not be cookies-related but not resetting forms properly. Alas, after I posted.

I have uncovered a suitably ancient solution for your benefit. Vintage, almost, from the distant year 2010. I hope is old enough to not make you freak out :)))) (hehehehe) https://stackoverflow.com/questions/2559616/javascript-true-form-reset-for-hidden-fields . The first I would try would be the 1st answer, but it was written on Fools Day. So fingers crossed.