User tag issue with server-side attribute

[Vakho]

Hello, 
 we've put the user tag into the HTTP requests and the Client app will provide information for all requests to the API endpoints once the user has logged in.  I've created the rule to catch from client-side HTTP request value with x-user.
For 90% of all users it can identify and fetch the usernames but sometimes I'm getting Anonimus users as well, what might be the issue? 
We use JWT for authentication and follow up the username as text in the HTTP header. 

Also, some of the user names are shown with symbols but they are not using any symbols as it's restricted in the app. 
The example of the symbolic username is this: �ve C�t�

[DanielS]

Hello, from my experience, if users use browsers with private mode, it can't be captured and these requests come out as anonymous.

[Vakho]

Hello DanielS, 
Does private mode in the browser limit HTTP requests as well? If the username is followed into the HTTP requests from the client side, should it anyway be included, or private mode limits it somehow? 
So, the solution would be to go with the server-side just to be sure? or did you use any other solution to fix it? 

Thanks

[DanielS]

Hi@Vakho not exactly the requests but could also rip part of the data because cookies and site data not stored. What I am trying to say is to generate a test case for this and see if this is the cause. Use same browser and same user and see if it happens because of private.