Error with form submission in some courses

In some courses, like this->(https://www.memrise.com/course/66405/quenya-tolkien-elvish/) one, in level 16, word 1(’-’ = ‘aorist A-stem verb’), when you have to type in the ‘-’, it marks it as wrong due to the fact there is no alphabetic letters in the answer. Then when you type in the ‘-’ afterwards (after you have got it ‘wrong’) it will be green, but pressing ENTER on your keyboard doesn’t submit the answer, and you have to click ‘See Answer’ or ‘Next’. I don’t like this, because it marks it as wrong even though it is correct.