Tested on both Mac (12.1) and Windows (11), it does not happen on Windows so it looks like a MAC specific issue.

To reproduce:
Use the standard QCompleter example
https://doc.qt.io/qt-5/qtwidgets-tools-completer-example.html

Add "春风" (copy & paste from here should be OK) to the top of wordlist.txt. Compile and Run.

Select Model to WorldList. Select (Chinese)Pinyin input method. Type "chun" and confirm as "春", this should open the completer drop down list, which is the expected behavior. But:

1) when the drop down list is open, the selection list of the input method is hided (or not showing at all)

2) when there is unconfirmed input and click another editable widget. It opens the drop down list.

3) it takes 2 clicks to return the focus back to the original widget.

**Probably it worth checking other input method which has a selection list, and unconfirmed/confirmed status change.