Many user_ids associated with one idvisitor

Hi All,

Recently I’ve been noticing that we are getting lots of different user_ids assigned to the same idvisitor.

In the example below, I’ve done a SQL query which converts the binary held idvisitor to a bigint and the user_id is just a hashed value being sent through by website as their customer account number.

Has anyone else seen this and is there some setting which I am not using which is confusing the matomo system to thinking all of these visitors are bound to the same user?