[cynical]So if ALL other players are liars, just don't thrust liars, don't ask them for a map seed, they will lie ![/cynical]
We obviously are not playing the same game, on my PS4, the same name (and same 7DTD version) always gave me the same map.
If your 7DTD version works the way you describe it, I fear we cannot help you, as our version works "same seed == same map".
On which console are you ? And which is your 7DTD version (update number) ?