Visitor id from native app to webview

[#1]

I have a hybrid application, one part is native and the other part in webview.

As I told them, developers set the adobe_mc parameter in the url to track the VisitorID.

The problem is that the eVar where VisitorID is stored loses its persistence once user does the transition from native to webview app or vice versa.

Specific funnel example:

1 - the designed eVar is valorized (as a certain VisitorID number) in the native app;

2 - user goes to webview, than the eVar appears not to be valorized (eVarXX = "Unspecified");

3 - user finally comes back to native part and that eVar is valorized again as it was at the very start.

Could you help me?

Thanks in advance.

[#2]

1 & 3. In the following screens you can see the server calls of the native environment and of the webview environment.

     The first one is the native app server call, the second one is the webview call and the last one is a native server call.

    - native server call:

- web view server call:

- native server call:

      The mid parameter appears only in the webview server call (the second screen).

2. I set the value of the eVar only in the login in the native environment.

   In the Report Suite Manager I set the option "expire after" with the value never.

Thanks in advance.