CPU Stall, Sleep and Wait for Event

Before I rarely get this problems in the Editor. This profiling is from the PIE mode. When the game is cooked it doesn’t stall, sleep or wait for event, the performance is smooth. I think something is wrong with the editor?

Link for the profiling stats: UEDPIE_1_NightmareMap-Windows-20-11.36.41

Uploaded to mediafire due to 5MB max upload here in Answerhub. It is a 10 second profiling.

Processor: Intel Core i5-4690 3.50GHz
Video Card: Nvidia Geforce GTX 960
Ram: 8GB

I am currently experiencing this problem too. After a month of development, frame rate is suddenly running at 15fps with very large wait times for stalling. The project runs perfectly fine on other computers, and builds work perfectly fine on mine.