SharePoint Online List Experience - Default Experience

Hi,

I've logged in today whilst doing some work and all of our sub-sites (communication sites) that have libraries set to default list experience are now displaying in the classic experience when previously they were displaying in the new experience.  They were all displaying as expected yesterday, but only ones explicitly stated as "New experience" are ok today. Has anyone come across this recently? Is it a known bug that rectifies itself after a short time (a bit like the unmovable webparts)?

Is there a quick way to set libraries in the sub-sites to the new experience or will I need to go into each sub-site and change their library settings manually?

Cheers, 

Lee