a few day ago I have had the problem (SS 3.7.2) that there was a blank screen affter creating a new page - also when adding a new item to GridField. I have searched in the web for a solution and have seen that other people have the same problem too - but no solutions.
Here ist my solution… check all the PHP-files in “mysite/code”. If there is a blank character or space befroe the opening “<?php” of the file? Delete the space - That works for me.