I think a lot of companies with more limited resources have struggled with the jump from Android 7 to 8+. There are very significant changes in the hardware layer architecture.I can second that.
The Gemini is extremely instable on 8.1
I often have crashes in Edge or slower networks and battery worse than before.
The fact, that the batterymonitor doesn't work is even worse.
I hope, that they address these issues soon or I will have to go back to 7.1.