Unfortunately the bug depends on some Xiaomi firmwares, because of this there is nothing we can do to fix this problem. The issue affects Smart Launcher, like any other apps on Play Store that displays info about alarms.
The solution is to disable calendar events in Smart Launcher settings or to use an alternative widget in the home screen.
This behavior is consequence of a change in MIUI 11 and it's totally independent from Smart Launcher. Now you need to enable the option Display pop-up windows while running in the background (in Settings > Apps > Rights > Other permissions) for each widget you want to use on your home screen.
You can read more details on the Xiaomi official community
At the moment, there aren’t any other known issues about Xiaomi or Redmi devices, if you find any, please report the problem to email@example.com