Losing link to categories

I’m using the Linkview plugin for a small website for our small animal club where I rely on the links based on categories. For the third time a lot of links lost their relationship with their category. Because this can only be repaired editing the links one for one it is a lot of work. (It would be nice when editing can be done for multiple links at once.) I don’t know why en when these linked categories disappear … Hope someone has a clue …
Kind regards,
Roland

The page I need help with: [log in to see the link]