RBR750: Firmware upgrade V3.2.16.22_1.4.9: IP Configuration Failure

After reading a couple of forum posts, I tried to do an experiment: I reduced the DHCP range for the LAN and reserved IPs for some of the devices. With that done, after rebooting the router, these devices would connect reliabliy every single time. Right now, I seem to have about 40 odd devices & I reserved IPs for all of them. I've restarted my router a couple of times & even after that all devices seems to connect back. In fact, I left a few devices to use DHCP and they're working correctly as well.

I am wondering if there's a bug in the router's DHCP server module that fails to work if a lot of devices tries to connect to it at the same time requesting for IPs. This would be weird because we're talking about ~40 odd devices and not like ~1000s, causing some sort of a thundering herd problem. I'm not a network expert but this is my hunch so far. 

Any other ideas or experiments would be appreciated.

FURRYe38 : Yes I tried to reset by pressing the reset button for over 15sec. In fact, I've done it multiple times since yesterday. But none of these steps have helped me so far