There have been a couple of minor changes but this question is a little bit hard to answer without seeing your specific study and question. There was a change made to the .page class. previously the width was explicitly set to 900px no matter what and in Lighthouse we no set the width to 100% and the max-width to 900px. So the behavior you want may be as simple as adding
to your study. This will have negative ramifications to any of your respondents who are fielding your study on smaller screens which is the reason it was changed. But that's where I would start. If that doesn't work, we'll probably have to look at your specific question.