A Ma'mum leaving the row in Salah

Q 6: We are a group of worshippers who perform Salah (prayer) in the Masjid (mosque). One of the worshippers sometimes moves forward a little so that the row appears to be uneven. We advised him, but he keeps doing this, we do not know whether it is intentional or not. Is our Salah valid?

(Part No. 8; Page No. 16)  A: Your Salah is valid and you have to continue advising this man.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.