New Poco X3 NFC many bugs since MIUI 12


Aug 6, 2021

Here is my phone specs:
Poco X3 NFC
Android 11 RKQ1.200826.002
Miui Global 12.0.8 Stable (RJGEUXM)

Bought in september 2020 and was working very well, amazing phone !

But, since Miui 12 update (and maybe Android 11 ?!), it seems to be a lot of bugs what I never had before:
1. I have apps' logo in cercles AND squares forms, so it's definitely not esthetic view. Plus, sometimes an app' logo is cercle, and sometimes it's becoming a square... This problem appeared just after the Miui 12 update.
2. My micro SD card is not recognized anymore by a lot of apps. My DCIM file is on it. When I open an app like Facebook and want to share a picture, I search into files explorer, select the picture or video, and nothing happen. Same problem with a looot of apps. If I go to the Miui Explorer, SD card, DCIM, to search for the picture/video, I select "open with" and then it's not suggesting any apps but saying that I'm not allowed, I have to contact my system administrattor ??????? Such like Windows administration system ?!
3. I ain't got no home connexion in my house (countryside), so I use my 4G (LTE) signal to connect at home. I left for 10 days my house where I usually get 4G with very good signal 4/5 on Band 800Hz (B20) which allow me to easily watch streaming (Netflix, Youtube, Molotov...). When I came back for the weekend, the phone couldn't get any signal. I downloaded NetMonster and I realized that the phone was trying to connect to 4G antenna which is 18km away while I have a 4G antenna 5km away !!! So I could get a little 1/5 4G signal on the 2nd floor of my house and under the window ! Rest of the time I had a little 3G (H) or nothing at all ! When in 3G, it was connecting on 900Hz band to antenna closed to my house.
I did try to put on airplane mode for few seconds, put back on connecting mode, but nothing changed.
I did try to restart the phone, nothing changed.
I did try to stop the phone, to start again, nothing changed.
I was about to save my files and format the phone. I left the phone during one night on airplane mode. In the morning I had very good 4G signal again ! The phone finally managed to connect to the 4G antenna closed to my house ! We can check online troubles on antennas, and there was no troubles on antennas around my house so the problem was coming from the phone ! Plus, sometimes the phone is showing 2/5 4G signal but cannot connect to internet, for example Chrome is saying "no network" (same with some other apps). I put on airplane mode few seconds, and then it's finally showing a 2/5 3G signal...! It seems the phone antenna has a software bug or maybe the hardware is dying ??? It's happened once but I'm scared it's happening again, because I can't call or use internet in my house without my phone !!!
4. One very very annoying bug what I already had on Redmi 3S pro and Redmi 6 pro ! Each time I had to change the piece to solve the problem. it's about the main microphone which is not working anymore. When I call with the original Call app of the phone, people don't hear me, but if I click on Speaker during the call, then they can hear me but low, like I'm "far", because when the speaker is on, there's the second microphone ("ambience" mic) which is on ! If I call with WhatsApp, neither main nor second microphone are working so I cannot call anymore with WhatsApp ! Compared to Redmi's microphone problems what I had, with the Poco I can still use Music apps to recognize what music is on the radio (Shazam, Deezer), which means the main mic is working well ! So I wonder if it's a software bug or like Redmi's a hardware failure ???
5. When texting a message, whatever apps, sometimes some letters are not working on the virtual keyboard (Swiftkey), sometimes, i, sometimes o, sometimes SPACE bar... Anyway, in this case I have to restart the phone, that's the only way that the keyboard is working again !

Phone is still under guarantee for 1 or 2 months.

I'm about to downdate the phone to MIUI 11 with factory setup.
If you guys have any ideas, let me know, thanks.