Draw Material use HUD conflicts with showing Material in Image of UMG

I draw a Material in HUD using the function HUD::DrawMaterialSimple, and I use a UMaterialInstanceDynamic as parameter, then I use Image of UMG to show a UMaterialInstanceDynamic in widget at the same time. Now strange thing happen, the Image in widget cant show any thing. if I dont draw Material in HUD or draw some thing else (like a line or texture…) after drawing the material the Image can show normally, Anyone else in this trouble? who can help me.

Anyone can help me? don`t be scared of my poor English.

I have simular problem. Search in web can’t help me.