I ran into this problem recently with a new 5070 image I created for our organization. Some poking around showed there is something at startup that runs a batch file that checks for the presence of C:\Users\Public\Documents\Wyse\first_boot.txt and, if the file is present, launches the quick start page. Used a command file in an app policy to delete this text file and the page no longer launches on startup. For future images, I’ll make sure the file is deleted prior to sysprep.