I'm running macOS 10.14.3 Beta (18D32a) on a (2018) 13" MBP i5/16/256 and just recently started using iMovie 10.1.10 (330236) and noticed that it constantly freezes up and crashes. It works fine initially, but about a minute later everything gets super laggy to the point where the entire system before frozen. What could be the cause of this?