Unreal Engine 4.21 Preview

hello , am getting thing this bug in unreal 4.21 and 4.20 , the problem is alot of compile shaders when changing preview too mush , as you can see

in the photo that i upload it , please report or help me fix this bug that wont allow me to use material editor cuz its too slow ,
my pc
GTX 1070
I5
16GB ram
Windows 10
and thanks!