Ads Stuck in 'Preparing' or 'Active' and Not Delivering

Is anyone else having this issue? Started happening for everyone in our business manager from ~36 hours ago. Some assets run, others stay in 'Preparing' or become 'Active' and don't spend. Duplicating or editing the ads has been working with varying degrees of success, some still stay stuck. We manage >300 ad accounts and we're seeing this across all accounts. All ads posted prior to yesterday are running OK.