Quote - set to emit a single photon.  Now, according to Relativity, there is only one photon,

You said Relativity and here is the problem. Relativity ignores Quantics, Electromagnetism and the wave nature of light.
A single "photon" can pass through two holes at the same time and worst!.... an electron also can do it!
Relativity is a limited theory with a limited scope of application. A simple phenomena as difraction of light is impossible to happen for Relativity.

And Yes, God do play dice and Devil can do even worst things...

Stupidity also evolves!