Problem with UI refresh/Session Management running Vaadin application in se

I developed a Web Application (Front-End for a Database) in Vaadin 8.5.2. It is deployed on a server, using tomee.
In my UI, I have a tabsheet with three tabs, each displaying on top a Data Grid, and on bottom another TabSheet containing textFields, Comboboxes etc. to display and Edit Data. When selecting a row in the Grid, the bottom TabSheets GUI Elements are updated.
When I start the application in two browsers (no matter if in one ore two browsers, or two computers), the UI of the tabsheet ob the first started application is updated, the UI of the second one not (in spite of the fact that the data are required and processed correctly). astonishingly, this difference occurs not due to loading the application but due to loading the tab.
So: Application 1, selecting in TabSheet 1 → Data displayed correctly
Application2, selecting in TabSheet 1 → Data not displayed
changing to TabSheet 2 in both applications
Application 2 selecting Data in TabSheet 2 → Data displayed correctly
Application 1 selecting Data in TabSheet 2 → Data not displayed.
In one of my bottom tabsheets I have a Upload with image (with UploadExample class as model), used to upload Images (stored as byte) and to display selected images in the DB (or a dummy in case of DB Cell being null).
This Tool works fine in any Application I start in FireFox (although other Tools are not updated!), in Chrome it is not shown in the second started Application.
I do not understand this behaviour (Session Management? UI Refresh?) and thus would highly appreciate any recommendation how to fix this.

Thank you in advance!

My problem is solved: I found a recommendation about not to save GUI Elements in static Fields; indeed I had, and after changing this by storing my elements in a ApplicationContext class, it works.