Cisco 819 acting like DHCP pool is full even when it's not?

We've had several issues where when we add devices to our network, we have to expand the DHCP pool in order for that device to get connected. However, there's always been enough addresses available in that pool.

Setup: Cisco 819 router, and from that an un-managed dummy Netgear switch, in which these devices are being plugged into. The switch we have set up as Vlan2, which has direct internet access. We normally have the DHCP pool range of 192.168.2.245 to 192.168.2.253, with 192.168.2.254 being the IP of the Vlan itself. So, in my mind there should be 9 available IP addresses. However, on some occasions there have only been 4 or 5 devices in that Vlan, and the new device won't get connected until after we expand the DHCP pool. We've tried restarting the switch, the router, clearing DHCP binding and the ARP table. What else could this be?

Some config:

ip dhcp pool manager network 192.168.2.0 255.255.255.0 default-router 192.168.2.254 dns-server x.x.x.x x.x.x.x lease 3 class MANAGER address range 192.168.2.241 192.168.2.253 (This is what we expand it to. Typically the range starts at .245) 

Config for the Vlan:

interface Vlan2 ip vrf receive INET ip vrf receive INET-CELL ip address 192.168.2.254 255.255.255.0 ip access-group 150 in no ip redirects ip nat inside ip virtual-reassembly in no ip route-cache ip tcp adjust-mss 1300 ip policy route-map LOCAL-INTERNET hold-queue 32 in Extended IP access list 150 10 deny ip any 10.0.0.0 0.255.255.255 20 permit ip any any (1540064 matches)