Tā zuìjìn jiālǐ yǒushì, qíngxù yìzhí bútài wěndìng.
He's had family matters lately, and his mood has been unstable.
Tips
usage
有事 is a very common polite way to decline invitations without giving specifics - like saying 'I have something to do' in English. The opposite 没事 (méi shì) means 'no problem' or 'I'm fine.'