I became so frustrated with the wretched thing on one site that I complained. I received a kind reply saying that they are trying to find something better to beat the 'cheats' which should arrive in the next few weeks. I may well lose the will to live before that happens so I am keeping off ayything which uses those just in case!
I saw that someone else further up said that even though you absolutely know you got it right it still does not accept it and let you through. And when it patronizes you after that with a 'Please try again' I could become incandescent so not good for the blood pressure!
Anger management!!! Help needed.