try turning off MIUI gestures and use Fluid Gestures (https://play.google.com/store/apps/details?id=com.fb.fluid&hl=en)
maybe it will work better for you.
Also i noticed when you turn off animation in MIUI gestures settings it work a lot faster.
This bug with front camera portrait mode on stable MIUI10 is main reason i switched back to MIUI10 beta, now it's back to normal.
Now my question is, did anyone managed to make back (main) camera portrait mode working with MIUI? (with or without HDR)
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What do you mean? I use 2 sim cards, one 4G for internet, one 3G for voice calls. During the trip all was at default, plus sometimes I used train's free wifi. As i did mainly reading and some photography i turned on battery saver feature.
heres mine GPU profiled. 3GB RAM/32GB ROM version, MIUI 10 by XIAOMI.eu 8.9.6
try changing transition effects in launcher, noticed a little lag when changing transition to anything other than default. but not sure if we're speaking about the same thing.