Hello ,
Unfortunately, I can’t say exactly what steps I took. I just played around the blueprints, so I spent all time in the main editor and BP editor. I worked for 6 hours. After 5-th hours I noticed performance problem of my laptop (Core I7 2.4GHz, 16 Gb RAM, NVIDIA NVS 5400M, SSD, Win7 x64) and looked into task manager.
I noticed that any kind of changes leads to increasing memory consumption (maybe this is the clue).
I’ll try to reproduce this issue again.