Your project looks correct. The source files are UTF8 which is correct. What happened during the 30 minutes after you closed the project and before you reopened it again? Did you load source files into another editor which could have corrupted the encoding? If you now edit the label texts to replace the wrong characters and save and reload again do the labels remain correct or are they corrupted again?
Did you load source files into another editor which could have corrupted the encoding?