As northernguy says below.. you need to listen to both slow and fast.. the slow say each word individually therefor - singular and plural sound the same.. when you listen to it fast you here it said as a sentence which clearly gives you the S sound at the end of "Leurs" I will say though sometimes the audio on this thing can be pretty bad, but this one is ok.
Couldn't make out leur at high speed so played at slow speed which made it quite clear. Got it wrong because it's leurs enfants not leur enfant. On being corrected I listened to it again and clearly heard the s sound at the end of leurs sliding into enfant on the high speed track which was definitely not there on the slow speed track.
Must remember to go back to the high speed track after sorting out any confusion at slow speed because the information on the high speed is what Duo marks on.