An update. Again this issue appeared. Everything was working properly then all of the sudden all other public IP addresses other than the Static IP the router is using stop working and users get a gateway timeout error. I was able to get it working ...
I had this exact same problem. I have multiple public IPs from my ISP. I need to foward ports from different IPs to different machines such as 1.1.1.27:80 goes to 192.168.1.50 and 1.1.1.27:443 goes to 192.168.1.511.1.1.28:80 goes to 192.168.1.52...