This is in our generated.cpp which contains the classes which the mismatch is referring to.
NIX
FGuid Guid;
Guid.A = 0xE105D02F;
Guid.B = 0x224EB91D;
Guid.C = 0x00000000;
Guid.D = 0x00000000;
ReturnPackage->SetGuid(Guid);
WIN
FGuid Guid;
Guid.A = 0xE105D02F;
Guid.B = 0x224EB91D;
Guid.C = 0x00000000;
Guid.D = 0x00000000;
ReturnPackage->SetGuid(Guid);
OSX
FGuid Guid;
Guid.A = 0xE105D02F;
Guid.B = 0x224EB91D;
Guid.C = 0x00000000;
Guid.D = 0x00000000;
ReturnPackage->SetGuid(Guid);