I am using redmi 12C. The issues I faced are,
Issue with the adaptive display brightness. The reason seems to be that it doesn’t have a dedicated light sensor. So, it uses its front-facing camera to detect ambient light. That happens only when it turns on the display. At that point it adjusts the display brightness and then remains at that constant setting, irrespective of the changes to the background light. The worst case is when you are out in full sunlight, and you get a call while your phone is in your pocket. Then before you get your phone out, it sets the display to the lowest brightness setting since it is in darkness (inside your pocket). Once you get it out you see nothing. Really annoying. Check this
Other bad thing I experience is that, once you receive a call it rings but sometimes it doesn't show the dialer app to answer the call. Sometimes you can go to the notification area and click on the call notification and get it. This too is really annoying. No firmware update has resolved this.