ios forget password from ldap

Hi! What you say about iOS devices with freeradius and unifi? Many people in our office saying their iOS devices forgot password from ldap account and every week (or few days) they write again and again their passwоrds to connect to the network (which is saved on they devices and must remeber credentials and automaticly connect as soon as they walk in office)   Unifi — freeradius — ldap   i use ttls+pap   who guilty in this case?