Crash when I set effect in medium or low

when I set the effects on Low or Medium from settings Unreal Engine crashes.
The same thing happens if from Blueprint I use “Set scalability Quality to Low” or “Set scalability Quality to medium”.
how can i solve?
Thanks in advance!

This is because of compiling, when you select medium or low, then Unreal Engine 4 need to recompile all settings,

You can try to select one setting att the time, like first take shadow then textures etc…

Tell me if you need more help