GridLayout misbehaving in Vaadin 7

I am currently migrating from Vaadin 6 to Vaadin 7, and the problem I have at the moment is that my login screen is incorrectly displayed. What my problem looks like can be seen in the attachments (Login_korr is what the layout should look like). After 2 days of trying every suggested fix I could find, I still have no idea why the GridLayout behaves like this. I tried doing it with a VerticalLayout, which worked, but is too much to change, because the layout issue is in every spot a GridLayout is used.
The following code is everything that happens on the login screen:

public Login()
{
Login.setLocaleLanguage(Login.getLocaleLanguage() != null ? Login.getLocaleLanguage() : Locale.GERMAN);
nba = (NBA) AppModel.getApplication();
uiFactory = new UIFactory();
defineServices();
VerticalLayout verticalLayout = buildMainLayout();
chbMerken.setValue(false);
if (nba.cookieSessionId != null && nba.cookieSessionId.length() > 0 && nba.cookieUserPk != null && nba.cookieUserPk.length() > 0) {
try {
userByPermSessionId = userService.findZ_userByPk(Integer.parseInt(nba.cookieUserPk));
} catch (NumberFormatException | BNException | EJBTransactionRolledbackException e) {
}
// now compare saved SessionId with cookie-sessionId, if return-Object isn't null
if (userByPermSessionId != null && userByPermSessionId.getPermsessionid() != null
&& BCrypt.checkpw(nba.cookieSessionId, userByPermSessionId.getPermsessionid())) {
// check, if permission is expired
if (DateFunctions.getUTCDate().getTime() <= userByPermSessionId.getPermsessionexpiration().getTime()) {
tfUsername.setValue(userByPermSessionId.getLoginname());
pfPassword.setValue(" ");
chbMerken.setValue(true);
}
}
}

// setSizeFull();
setSizeFull();
verticalLayout.setWidth("500px");
addComponent(verticalLayout);
if (lbPoweredByOouyea != null) {
mainLayout.setComponentAlignment(lbPoweredByOouyea, Alignment.TOP_CENTER);
}
setComponentAlignment(verticalLayout, Alignment.MIDDLE_RIGHT);
}

private VerticalLayout buildMainLayout() {
        // common part: create layout
        mainLayout = uiFactory.createVerticalLayout();
        mainLayout.setStyleName("megavl");
        mainLayout.setSpacing(true);
        mainLayout.setMargin(true);

        // top-level component properties
         setWidth("100.0%");
         setHeight("100.0%");

        // gridLayout_1
//        GridLayout gridLayout_1 = buildGridLayout_1();
        GridLayout gridLayout_1 = buildGridLayout_1();
        createAndAddLogo(nba.defaultTheme);

        Label spacer = uiFactory.createLabel(null);
        spacer.setHeight("20px");
        mainLayout.addComponent(spacer);

        Panel pn = uiFactory.createPanel("");
        pn.setStyleName("megapanel");
        pn.setSizeFull();
        pn.setHeight("300px");

        VerticalLayout vl = uiFactory.createVerticalLayout();
        vl.setSizeFull();
        vl.addComponent(gridLayout_1);
        vl.setComponentAlignment(gridLayout_1, Alignment.MIDDLE_CENTER);

        pn.setContent(vl);
        mainLayout.addComponent(pn);
        
        //VERSUCH
        mainLayout.setComponentAlignment(pn, Alignment.MIDDLE_CENTER);

        createAndAddPoweredby();

        return mainLayout;
    }

public VerticalLayout createVerticalLayout(String styleName) {
        VerticalLayout result = new VerticalLayout();
        result.setImmediate(false);
        result.setWidth("100.0%");
        result.setHeight("-1px");
        result.setMargin(false);
        result.setSpacing(true);
        if (styleName != null) {
            result.setStyleName(styleName);
        }
        return result;
    }

private GridLayout buildGridLayout_1() {
        // common part: create layout
        GridLayout gridLayout_1 = new GridLayout();//uiFactory.createGridLayout();
        gridLayout_1.setSizeFull();
        gridLayout_1.setSpacing(true);
        gridLayout_1.setMargin(true);
        gridLayout_1.setStyleName("logingrid");
        gridLayout_1.setColumns(2);
        gridLayout_1.setRows(8);

        Label caption = new Label("Anmeldung");//uiFactory.createLabel("login_title");
        caption.setStyleName("loginheadline");
        gridLayout_1.addComponent(caption, 0, 0, 1, 0);
        gridLayout_1.setComponentAlignment(caption, Alignment.MIDDLE_CENTER);

        // lbBenutzername
        Label lbBenutzername = new Label("Benutzername");//uiFactory.createLabel("benutzername");
        gridLayout_1.addComponent(lbBenutzername, 0, 1);
        gridLayout_1.setComponentAlignment(lbBenutzername, Alignment.MIDDLE_RIGHT);

        // tiBenutzername
        tfUsername = new TextField();//uiFactory.createRequiredTextField(null, null, 30);
        tfUsername.setCursorPosition(0);
        tfUsername.setStyleName("loginform");
        // tiBenutzername.setWidth("250px");
        gridLayout_1.addComponent(tfUsername, 1, 1);
        gridLayout_1.setComponentAlignment(tfUsername, Alignment.MIDDLE_LEFT);

        // lbPasswort
        Label lbPasswort = new Label("Passwort");//uiFactory.createLabel("passwort");
        gridLayout_1.addComponent(lbPasswort, 0, 2);
        gridLayout_1.setComponentAlignment(lbPasswort, Alignment.MIDDLE_RIGHT);

        // tiPasswort
        pfPassword = new PasswordField();//uiFactory.createPasswordField();
        pfPassword.setStyleName("loginform");
        pfPassword.addShortcutListener(new ShortcutListener("Shortcut Name", ShortcutAction.KeyCode.ENTER, null) {
            private static final long serialVersionUID = 3601642341705694472L;

            @Override
            public void handleAction(Object sender, Object target) {
                checkLogin();
            }
        });
        gridLayout_1.addComponent(pfPassword, 1, 2);
        gridLayout_1.setComponentAlignment(pfPassword, Alignment.MIDDLE_LEFT);
    
        // password reset
    HorizontalLayout hlResetPassword = new HorizontalLayout();//uiFactory.createHorizontalLayout();
    hlResetPassword.addLayoutClickListener(new LayoutClickListener() {
        private static final long serialVersionUID = -6131089921825563746L;

        @Override
        public void layoutClick(LayoutEvents.LayoutClickEvent event) {
        
        passwordReset();
        }
    });
    
    lbResetPassword = new Label("Reset Password");//uiFactory.createLabel("reset_password");
    lbResetPassword.setDescription(Messages.getTooltipString("login_reset_password"));
    
    if ("!reset_password!".equals(lbResetPassword.getCaption())) {
        lbResetPassword.setCaption("Passwort zur\u00FCcksetzen");
    }
    hlResetPassword.addComponent(lbResetPassword);
        hlResetPassword.setComponentAlignment(lbResetPassword, Alignment.MIDDLE_CENTER);
    gridLayout_1.addComponent(hlResetPassword, 0, 3, 1, 3);
        gridLayout_1.setComponentAlignment(hlResetPassword, Alignment.MIDDLE_CENTER);
    
        // chbMerken
        chbMerken = new CheckBox("Daten merken");//uiFactory.createCheckBox("datenmerken");
        gridLayout_1.addComponent(chbMerken, 0, 4, 1, 4);
        gridLayout_1.setComponentAlignment(chbMerken, Alignment.MIDDLE_CENTER);

        // btnAnmelden
//        btnLogon = uiFactory.createEnabledButton("anmelden", new ClickListener() {
        btnLogon = new Button("Anmelden", new ClickListener() {
        
            private static final long serialVersionUID = -8263590240563130212L;

            @Override
            public void buttonClick(ClickEvent event) {
                checkLogin();
            }
        });
        btnLogon.setStyleName("loginbutton");

        gridLayout_1.addComponent(btnLogon, 0, 5, 1, 5);
        gridLayout_1.setComponentAlignment(btnLogon, Alignment.MIDDLE_CENTER);

        // Language switch buttons
        HorizontalLayout hlLanguages = new HorizontalLayout();//uiFactory.createHorizontalLayout();
        hlLanguages.setSizeUndefined();

        addLanguage(hlLanguages, "Deutsch", Locale.GERMAN);
        hlLanguages.addComponent(new Label("|"));

        addLanguage(hlLanguages, "English", Locale.ENGLISH);
        hlLanguages.addComponent(new Label("|"));

        addLanguage(hlLanguages, "slovenia", new Locale("sl", "SI"));
        gridLayout_1.addComponent(hlLanguages, 0, 7, 1, 7);
        gridLayout_1.setComponentAlignment(hlLanguages, Alignment.MIDDLE_CENTER);

        return gridLayout_1;
    }

Thanks in advance