Firefox sometimes ignore language setting and set to device language

I'm using Firefox latest version 128.0, device language was set to Japanese but I set Firefox 's language to English (United Kingdom) or English US. However, if I press home button (the Android button) to go back to home screen (the Android main home screen), or rotaing firefox window, firefox will ignore set language (english) and now set to follow device language (Japanese) however, if you go to menu -> settings, language (言語 gengo, language) it was checked to english uk. I dont know what happened?