Built splash screen looping

Hi. I have built projects in the past successfully. Then all of a sudden, I made a build successfully (development - but this happens with release as well). When I run the EXE the Unreal splash screen fades in, fades out… and then again and again forever. I’ve tried pressing various keys to advance the screen but it keeps looping. I have to Alt+F4 to quit. I am building to Drive C:/ and there are no errors or related warnings in the log. When I use a blank template project (shooter) the build is successful and the game starts up normally. However, on my projects using the MFPS template (their demo, and my version).
Any ideas of what is causing the looping? Using Unreal 5.1 on Windows 10 pro. Thanks!