Problem with Randomising uploaded headers

I have a website with 2 languages, English and Chinese. If I select "Randomising uploaded headers" for "Entire Site" on customizing header image, it works only for the default English webpages. On all Chinese pages (switched by language switcher) there is no any header image. However, if I select a fixed header image for "Entire Site", it works for both language pages. Could you please let me know how to solve the problem? Thanks!