Modules re-appear when switching language

[ChrisH5]

When switching languages, modules that shouldn't be appearing on that page will re-appear, what have I done wrong? They don't show if I go to the articles from the menu/links but when switching to the associated articles modules that should only show on the home page will re-appear.

More details;
I added a new main menu item in both langs which goes to an article (and all the home page modules will disappear and one or two modules that I want will appear), and the switching between languages works fine. That main article links to others in the same category and they display fine, but when switching languages on these articles all the home page modules will re-appear, the right article will still display below these modules but it's obviously not ideal.
It seems to work fine with other categories or articles, so what have I done wrong?

http://www.ysgolplasmawr.cymru is the site and it's the things under the CRASP menu item if anybody wants to take a look and I appreciate any help given.
Edit - I can see the links from the language switcher is missing "crasp/"....why?