We have investigate this here and have applied a fix for this issue. It seems to be an initialization issue with setting the pages visible to false initially. As a temporary workaround, you'll need to set each page container visible property to false, except for the active page.
No you only need to do this once in the constructor of the form, until the next version is available ofcourse. The next code loop should help you with this.
procedure TForm1.FormCreate(Sender: TObject);
var
I: Integer;
begin
for I := 0 to TMSFMXPageControl1.Pages.Count - 1 do