I got stubbornly eager to keep working in my video game and downloaded the latest ue4 version… that move somehow bypassed the issue…though 4.14 and 4.15 are far worse versions than 4.13.1 was. Currently in 4.15, it takes ages to make changes in my level blueprint…and of course sudden crashes are still frequent…but for this old crash I cannot provide more info right now…might you want reports from 4.15 instead?