Check under security app for auto started apps. You can also disable one apps at the time to pinpoint which app causes the wakelocks, since you don't have root.
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Do you have any Bluetooth device connected to your phone? Or smart Bluetooth unlock on? I found a Bluetooth caused kernel wakelocks on my redmi3 when I used smart unlock with miband.
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Yes. You can root official ROM with locked bootloader. There is a guide on en miui forum for it. Headover then to download the apk . install and run the app then you will have root access :)
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