Right now, the app communicates with Amber through a few hard-coded default relays, so users have no options to change them. I was considering ways to ease this problem, like letting users select some relays or adding 127.0.0.1:4869 to the default list.

However, if other apps aren't having major issues, it might not be a relay connection problem. Amethyst and Primal are native clients, so they wouldn't use relays in the same way, but zap.stream is a web app and should be communicating through relays.