I’m doing the German 5 course, though I’m sure the issue exists in other courses and other languages.
Some phrases contain a non-breaking space (U+00A0 aka ) in place of a normal space (U+0020); the result is that typing the correct answer (with a normal space) is not automatically accepted as correct, though it is still accepted if the ‘check’ button is clicked.
It would be good to replace them all with normal spaces.
[As a test example, there is “Gitarre spielen”]