Application menu locale changed occasionally on macOS

Hello there, I developed a Qt application on macOS with Qt 5.15.2 and I found a weird issue about translations. The steps to reproduce the issue are as the following:

1.  open Settings and choose Language & Region   

2.  Add Russian and Japanese in the preferred language. For me, Simplified Chinese is my primary language. Rearrange the order of the rest languages and make English as the last one.  

3.  I loaded Simplified Chinese qm files for Qt framework and my app UI. 

3.  open my application and check UI locale, all is good and the language is Simplified Chinese.

4.  try to click application menu on the menu bar, open and reopen about dialog or something for several times, the translations for system menu items then became as Japanese. It is worth noting that this phenomenon can only reproduced in application menu.

I compiled the universal Qt library on myself and tested on several Macs(11.2, 11.6). It turns out the issue doesn't have any relationship with system version.