Extreme PUBG Lag Problem Please Please Please HELP Pls

Hello,
Thank you so much for jumping in this thread & I desperately need your help, kindly read on.

I was a happy satisfied user of POCO (with known touch issues) which I primarily bought for PUBG until last month.
SInce last month or from Vikendi Map update, during gameplay, my game LAGS or hangs for a second, it happens every second of gameplay. This is extremely irritating.
To overcome PUBG Lag issue, I tried following ways

1. Changing PUBG Graphics settings to from HDR to HD, Balanced and even smooth,
reduced frame rates – Didn’t work.

2. Uninstall & Install again – Didn’t work.

3. Hard Reset & Fastboot Install – Worked for gameplay of around 1 hour, again LAG

4. Installed Custom Kernel – Franco, Extreme, SDClang with Performance governor in Kernal auditor or Performance profile in FK manager app and other possible tricks- randomly smooth gameplay for sometime ( 20% of total gameplay), then again heavy lag.

5. Now installed MIUI Global Beta 9.1.10 – Not Working

6. Repair option within PUBG – didnt work

Funniest part we bought 2 POCO phones , other for my brother and without any issues or lag gameplay is perfect in his phone even on HDR and Ultra setting.
I’m not a die hard gamer, but I love to play PUBG for around 1 Hour in evening after work but this unfortunate event has ruined it.

I request you all fellow members, Kindly suggest me a way out of this to make my gameplay smooth again, or atleast suggest me a way to find out the cause behind this.

Thank you from the bottom of heart in advance .