DHCP server/relay/bootp relay not working with some devices

I am pulling my hair out on this problem because it seems that a lot of people have had this issue, but none of the solutions have worked for me. I've got an SRX100H2 on 12.3X48-D65.1 and running dhcp-local-server. Some clients are getting IP addresses, but some are just stuck in SELECTING. I've narrowed this down to mostly iPhones, but it does affect other devices. I've tried setting the hidden command 'no-unicast-replies', but this does not help. I've tried configuring dhcp-relay and bootp helper mode to relay to a remote DHCP server and nothing seems to work.

#show system services dhcp-local-server 
group vl13 {
    interface vlan.0;
}

#show access 
address-assignment {
    pool vl13-dhcp {
        family inet {
            network 172.21.1.0/24;
            range r1 {
                low 172.21.1.32;
                high 172.21.1.254;
            }
            dhcp-attributes {
                maximum-lease-time 86400;
                server-identifier 172.21.1.1;
                domain-name domain.com;
                name-server {
                    x.x.x.x;
                    x.x.x.x;
                }
                router {
                    172.21.1.1;
                }
            }
        }
    }
}

#show security zones security-zone trust 
host-inbound-traffic {
    system-services {
        bootp;
        dhcp;
        ping;
        traceroute;
        ntp;
        snmp;
    }
}
interfaces {
    vlan.0;
    lo0.0;
}
interfaces {
    vlan.0;
    lo0.0;
}

# run show dhcp server binding 

IP address        Session Id  Hardware address   Expires     State      Interface
172.21.1.44       1664        30:6a:85:7c:7e:9a  10757       BOUND      vlan.0              
172.21.1.42       1662        78:8a:20:08:e0:90  10590       BOUND      vlan.0              
172.21.1.35       1655        a0:c9:a0:c7:a1:71  10003       BOUND      vlan.0              
172.21.1.43       1663        d0:df:9a:ef:3b:e3  10595       SELECTING  vlan.0              
172.21.1.34       1654        e4:e1:30:c5:35:c3  9924        BOUND      vlan.0              
172.21.1.41       1661        f8:95:ea:71:5a:07  10529       SELECTING  vlan.0