Playing as Egypt, I had already settled Memphis and Nekken, and made a promise to Tomyris not to place other cities too close to her. Then I settled Thebes and Akhetaten and made a similar promise to Saladin. Later, I finally filled a spot in the middle by settling Sais — but after doing that I was immediately denounced by both Scythia and Arabia! Why? Because I placed a city only four tiles away from my capital, and farther from those other Civs than my earlier cities! Does that make any sense?