It seems as though the multiple text answers for text fill in blank question does not work in my program.

I created a text question that requires one answer. There is more than one possible correct answer. I added these answers under correct answers as separate entries, however they are not seen as correct. As soon as I only have one correct answer it works. When I add an extra possible answer, the answer is not recognised. I tried it with the following answers: 5m; 5 m; 500cm; 500 cm

Is this a bug? Is it only my program that has gone crazy? Am I doing something silly?