Since it's unlikely to be something inside your computers, probably it's something in the network. Contact a professional network company to fix it.
I have a call center with over 400 computers, one router and the network is LAN, the problem is that the computers keeps on losing IP Address.
during morning hours they are ok but after sometime most of the lose their ip adress since its dynamic.
I tried running commands ipconfig /release, ipconfig /renew, ipconfig /flushdns, ipconfig /registerdns but its not working. kindly assist on how to solve this issue THANK YOU

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic