I believe, this is related to the DocumentsUI.apk problems. Try this solution (I can't post Links!) : look into the "MIUI Weekly Rom Releases" Forum, Subforum "6.8.25" and search for "DocumentsUI.apk". The relevant post is post # 513 from user @ingbrzy . He is offering an alternate...
I'm on 6.5.26 and switched off MIUI Optimization and RAM Optimization (both in Developer options) and Battery Life is very good. For me generally it lasts for 2 days.
Hello, how did you replace the DocumentsUI apk? I tried to replace it in system/app/DocumentsUI, but then I got an error: app Documents not found. Is there anything else to do? I'm on Xiaomi Mi4c 6.5.26