My dhcp server is running amd64/4.3-stable, GENERIC kernel.

Clients on 192.168.250.0/23 use the "tftp-server-name" option.  When 
dhcpd starts, the first request from that subnet gets all parameters 
correctly; all subsequent requests, whether from the same client or 
other clients, receive all the supplied options correctly except the 
tftp-server-name value; dhcpd either doesn't give the option or gives 
the option value as null.  Other options and the other subnets/ranges 
work fine.  Basically, dhcpd only gives out the tftp-server-name value 
once, to the first customer. 

I installed isc-dhcp-server-3.1.0 package to see if the problem 
persisted.  Using the identical (almost) dhcpd.conf below, everything 
works fine with  the ISC dhcpd.  The only thing I added to dhcpd.conf 
for isc-dhcp-server to work was the "ddns-update-style ad-hoc;" 
parameter.  Each subnet listed below corresponds to a separate physical 
ethernet interface (no vlans, no IP aliases.)
---
#
# DHCP server options.
# See dhcpd.conf(5) and dhcpd(8) for more information.
#

authoritative;

ddns-update-style ad-hoc;
default-lease-time 86400;
max-lease-time 172800;

subnet 192.168.252.0 netmask 255.255.252.0 {
    range 192.168.254.2 192.168.254.253;
    option domain-name "playsecond.com";
    option subnet-mask 255.255.252.0;
    option routers 192.168.253.1;
    option netbios-name-servers 192.168.252.15;
    option netbios-node-type 8;
    option ntp-servers 192.168.253.1;
    option  domain-name-servers 192.168.252.11, 192.168.252.12, 
192.168.253.51,
192.168.253.54;
}

subnet 192.168.249.0 netmask 255.255.255.0 {
    range 192.168.249.100 192.168.249.110;
    option subnet-mask 255.255.255.0;
    option routers 192.168.249.1;
    option ntp-servers 66.42.62.246, 84.16.227.204, 149.156.24.40, 
200.80.18.131
;
    option  domain-name-servers 198.144.192.4, 206.13.28.12;
}

subnet 192.168.250.0 netmask 255.255.254.0 {
    range 192.168.250.25 192.168.251.253;
    option subnet-mask 255.255.254.0;
    option tftp-server-name "192.168.250.11";
    option domain-name-servers 192.168.252.11, 192.168.252.12;
    option routers 192.168.250.1;
    option ntp-servers 192.168.250.1;
}
---

-Glenn