Some end users do not have - intentionally - a determined locale setting in AR System user preference hence the locale depends on the browser setting.
Naturally such users would like to have the same IT homepage layout regardless wheter they log in with german/english or any other locale. With current implementation this is not possible as only the locale dependend layout is loaded and if not layout is found, the default layout is loaded.
User logs in with an browser with english locale and changes the IT home page layout. Layout is saved and each time the user logs in with an english browser the saved layout is used. However if the same user logs in with a german browser, the english layout setting is not found, hence the default is loaded. Now when the user changes the layout with german browser to his usual settings and saves the record, then the layout is fine if the user continues to use german browsers. If he switches back to an english browser, again the german record is not found hence the default is loaded.
This behavior is as designed.
OOTB there is no possiblity to create two/more layout records for one user, but it would be a nice feature, if all users could save their homepage layout depending on their locale.
With this feature there would be the additional benefit to have the possibility to create to different IT Home Page layouts aswell.
There is a workaround to export the existing layout record and import it again as new record and set the locale field dependend on the users needs however this is quite time consuming if you have many users requesting this feature.