Something has caused special file flags to be set on the file. The reason beind that change cound be a few things and I won't go into it, but you can clear it manually.
1) Login to the stack as root
2) start the cli and session into the affected member (if not the current master)
3) Check the flags:
root@sw01-access-10g-1b-b13:LC:2% ls -oal *.conf
-rw-r--r-- 1 root wheel - 100 Jul 18 16:15 bootpd.conf
-rw-r--r-- 1 root wheel - 98 Jul 18 16:15 cosd.conf
-rw-r--r-- 1 root wheel - 3943 Jul 18 16:15 ifinfo.conf
-rw-r--r-- 1 root wheel - 0 Jul 18 16:15 ifmdata.conf
-rw-r--r-- 1 root wheel - 929 Jul 18 16:15 inetd.conf
-rw------- 1 root wheel - 0 Jul 18 16:15 keyadmin.conf
-rw-r--r-- 1 root wheel - 3637 Jul 18 16:15 login.conf
-rw-r--r-- 1 root wheel - 0 Jul 18 16:15 named.conf
-rw-r----- 1 root wheel - 170 Jul 18 16:15 newsyslog.conf
-rw-r--r-- 1 root wheel - 65 Jul 18 16:15 ntp.conf
-rw-r----- 1 root wheel schg,sunlnk 548 Apr 14 2015 pam.conf
-rw------- 1 root wheel - 0 Jul 18 16:15 pam_radius.conf
-rw------- 1 root wheel - 152 Jul 18 16:15 pam_tacplus.conf
-rw-r--r-- 1 root wheel - 18 Jul 18 16:15 resolv.conf
-rw-r--r-- 1 root wheel - 695 Jun 29 19:10 syslog.conf
root@sw01-access-10g-1b-b13:LC:2%
4) clear the flags on the affected file and verify they have been cleared:
root@sw01-access-10g-1b-b13:LC:2% chflags 0 pam.conf
root@sw01-access-10g-1b-b13:LC:2% ls -oal *.conf
-rw-r--r-- 1 root wheel - 100 Jul 18 16:15 bootpd.conf
-rw-r--r-- 1 root wheel - 98 Jul 18 16:15 cosd.conf
-rw-r--r-- 1 root wheel - 3943 Jul 18 16:15 ifinfo.conf
-rw-r--r-- 1 root wheel - 0 Jul 18 16:15 ifmdata.conf
-rw-r--r-- 1 root wheel - 929 Jul 18 16:15 inetd.conf
-rw------- 1 root wheel - 0 Jul 18 16:15 keyadmin.conf
-rw-r--r-- 1 root wheel - 3637 Jul 18 16:15 login.conf
-rw-r--r-- 1 root wheel - 0 Jul 18 16:15 named.conf
-rw-r----- 1 root wheel - 170 Jul 18 16:15 newsyslog.conf
-rw-r--r-- 1 root wheel - 65 Jul 18 16:15 ntp.conf
-rw-r----- 1 root wheel - 548 Apr 14 2015 pam.conf
-rw------- 1 root wheel - 0 Jul 18 16:15 pam_radius.conf
-rw------- 1 root wheel - 152 Jul 18 16:15 pam_tacplus.conf
-rw-r--r-- 1 root wheel - 18 Jul 18 16:15 resolv.conf
-rw-r--r-- 1 root wheel - 695 Jun 29 19:10 syslog.conf
root@sw01-access-10g-1b-b13:LC:2%
5) Exit to the stack master and execut a commit full and quit.