Same on my Redmi 5A. I tried some versions of TWRP and every one of them gave me this weird smudge. I fixed it by flashing 8.11.1 miui official in fastboot mode by MiFlash
I'm not complaining. I'm just saying what happened to me. If i can't do it then what's the point of this forum? This update was destroying every version of TWRP that i tried and i don't know why, so i just reported it
If someone know how to make icon pack or miui theme that include that icons feel free to use it and share because icons in 8.8.3 update looks terrible
https://drive.google.com/open?id=1TmoXqe8Ze-4UdhgcVN2jNYc5UIFaFqJ5