I have different links that are targeting the same user. The link is generated by each category that has a menu associated with it. For example, I have CatA and CatB with a menu pointing to CatA and another pointing CatB

Example of the links

example.com/CatA/itemlist/user/1-AuthorA
example.com/CatB/itemlist/user/1-AuthorA

Do you know how I can fix this?

You have two choices
a) If you have a handful of users map each user into a menu seperate item.

b) You can also use K2's advanced SEF settings which can be found in K2's settings page.

If you have only a few users who enter content I would opt in for a.