When the selected value (connected to an app variable) is set to value not found in the option list, the first value of the list will be displayed, and we can't select that first value on the list.
Steps:
  1. create a dropdown field with option list of ["AAA", "BBB"]
  2. create a page/app variable with value of "CCC"
  3. connect the variable to the Selected value property of the dropdown field
  4. run the app in web app preview portal
  5. dropdown field will display "AAA" (but the connected variable is "CCC")
  6. click on dropdown list, and select "AAA" => connected variable remains at "CCC"
  7. click on dropdown list, and select "BBB" => connected variable changed to "BBB"
This happens on the Web App preview portal. Incidentally, the dropdown list appears to work correctly on my Android phone (Android 11, runtime 4.2.12)
Operating system and version: Windows 10
Web browser and version: Chrome 100.0.4896.127
App: 390924
Page in app: dropdown