Black screen on Samsung S10 while using Blit() function with Render outside safe area

I used Unity 2018.3.14 f1


I have a simple image effect working on Samsung S10. But after I change the setting to render outside the safe are the image effect part becomes black. Although I can fix it with switching Blit Type to Always. But if I change it to always, Google pixel series would show freeze screen till the image effect's over. Is there any work around way? Or it's a native bug? the attachment is the code and shader I use.