I guess the issue is just caused by your configuration.

First question: CPE510 is an outdoor AP best suitable for long distance p2p transmission. According to your description, it seems that you use it in an indoor environment? Is your guest house independent of your main house? How far is it between them and what about the LOS? More details about where you install it and the network topology(layout) condition are needed.

Second question: I would rather not configure CPE in repeater mode because it will totally cut off the bandwidth.

The distance between the CPE510, mounted on the outside of my house, to the guest house is approximately 400'. The signal level inside the guest house is good at the side of the guest house facing the CPE510 drops to fair in the far corners of the house. The speed is 60 mbs in the rooms at the front of the guest house (which is basically the limit of our internet connection) and falls to 40 mbs in the far corners. The CPE510 is connected to my in house dhcp router. By putting the CPE510 in AP mode it isolates the guest house network from the main house network. Which is desirable.

The issue is that the occupants devices (android phone, Iphone, mac book) lose the wifi signal on the far side of the guest house.

I initially wanted to set up a bridge network by having the CPE510's face each other, but that configuration did not work at all. Perhaps bridge mode is what I should be using, but I need more specific instruction how to configure each CPE510. I have an additional wifi router that I was going to connect to the network port on the CPE510 at the guest house, but I never go that far as I couldn't establish a connection. Perhaps I had the CPE510's too close together while doing the setup.

Also, do both CPE510 need to be in bridge mode? Or can 1 be in AP mode and the other in Bridge?

Please let me know what additional info you need and what configuration I should be trying so I can make this work.

Thank you.