"Choose options" and "Add to cart" exchanged

-- url of the page with the problem -- : bekijx.com/rcl/nl-be/webshop/category/56-albums.html
-- HikaShop version -- : 2.4.0
-- Joomla version -- : 3.4.1
-- PHP version -- : 5.6.7
-- Browser(s) name and version -- : Firefox/37.0

After import of some articles/items ... as a test... I get all the items in the front-end BUT where it should say "choose options" because there are options to choose from it says "Add to cart" and where there are no options to choose from it says "Choose options" in the button ...

I can not seem to find what is wrong ... the buttons (try to) do what they say ... so that far it is ok ... it just should say the other thing ...

ok ... I think I found it ...

in my import i did not set values for the characteristics ... therefore there were no characteristics in the main article ... I did set these in articles where there where no other options (they were the main articles and there were no variants)

changing the values for the characteristics seemed to solve the problem ... hope this saves someone a lot of searching ...