[SOLVED] Window glitches after redrawing with RedrawWindow or SendMessage(WM

I'm writing an application in C++ using the standard Windows API. It does some simple registry modification using buttons. When a button is pressed, it changes a label displayed at the bottom. To change it, I need to repaint the window (which automatically changes the label as needed). But when I redraw the window, it starts glitching. The static labels start flickering, and the buttons are missing altogether, but it stops after moving the window. Here is a GIF of it happening:

Here is my WndProc function:

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
    static HFONT s_hFont = NULL;
    HWND drive;
    switch (message)
    {
        case WM_COMMAND:
            {
                int wmId = LOWORD(wParam);
                // Parse the menu selections:
                switch (wmId)
                {
                    case IDM_ABOUT:
                        DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
                        break;
                    case IDM_EXIT:
                        DestroyWindow(hWnd);
                        break;
                    case APPLY_BUTTON:
                        SetRegistryValues(hWnd);
                        break;
                    case CDRIVE_BUTTON:
                        newDriveSelection = 0;
                        RedrawWindow(hWnd, NULL, NULL, RDW_INVALIDATE); // tried both this...
                        break;
                    case DDRIVE_BUTTON:
                        newDriveSelection = 1;
                        InvalidateRect(hWnd, hWndSize, NULL); // ...and this
                        break;
                    default:
                        return DefWindowProc(hWnd, message, wParam, lParam);
                }
            }
            break;
    case WM_CREATE:
        {
        const TCHAR* fontName = _T("Tahoma");
        const long nFontSize = 10;

        HDC hdc = GetDC(hWnd);

        LOGFONT logFont = {0};
        logFont.lfHeight = -MulDiv(nFontSize, GetDeviceCaps(hdc, LOGPIXELSY), 72);
        logFont.lfWeight = FW_MEDIUM;
        _tcscpy_s(logFont.lfFaceName, fontName);

        s_hFont = CreateFontIndirect(&logFont);
        ReleaseDC(hWnd, hdc);
        //s_hFont = (HFONT)GetStockObject();
    }
    break;
    case WM_PAINT:
        {
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hWnd, &ps);
            HWND CDrvButton = CreateWindow(
                L"BUTTON",  // Predefined class; Unicode assumed 
                L"Set to C: Drive",      // Button text 
                WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,  // Styles 
                20,         // x position 
                20,         // y position 
                156,        // Button width
                21,        // Button height
                hWnd,     // Parent window
                (HMENU)CDRIVE_BUTTON,       // No menu.
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND DDrvButton = CreateWindow(
                L"BUTTON",  // Predefined class; Unicode assumed 
                L"Set to D: Drive",      // Button text 
                WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,  // Styles 
                20,         // x position 
                53,         // y position 
                156,        // Button width
                21,        // Button height
                hWnd,     // Parent window
                (HMENU)DDRIVE_BUTTON,       // No menu.
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND quit = CreateWindow(
                L"BUTTON",  // Predefined class; Unicode assumed 
                L"Quit",      // Button text 
                WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,  // Styles 
                20,         // x position 
                125,         // y position 
                54,        // Button width
                21,        // Button height
                hWnd,     // Parent window
                (HMENU)IDM_EXIT,       // No menu.
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND apply = CreateWindow(
                L"BUTTON",  // Predefined class; Unicode assumed 
                L"Apply",      // Button text 
                WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,  // Styles 
                220,         // x position 
                125,         // y position 
                63,        // Button width
                21,        // Button height
                hWnd,     // Parent window
                (HMENU)APPLY_BUTTON,       // No menu.
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND the = CreateWindow(
                L"static", 
                L"ST_U",
                WS_CHILD | WS_VISIBLE | WS_TABSTOP,
                35, 
                82, 
                28, 
                17,
                hWnd, 
                (HMENU)(501),
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE), 
                NULL);
            drive = CreateWindow(
                L"static",
                L"ST_U",
                WS_CHILD | WS_VISIBLE | WS_TABSTOP,
                66,
                82,
                18,
                17,
                hWnd,
                (HMENU)(501),
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND selected = CreateWindow(
                L"static",
                L"ST_U",
                WS_CHILD | WS_VISIBLE | WS_TABSTOP,
                87,
                82,
                196,
                17,
                hWnd,
                (HMENU)(501),
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND newdrv = CreateWindow(
                L"static",
                L"ST_U",
                WS_CHILD | WS_VISIBLE | WS_TABSTOP,
                25,
                99,
                276,
                23,
                hWnd,
                (HMENU)(501),
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            SetWindowText(the, L"The");
            SetWindowText(drive, GetDriveLetter());
            SetWindowText(selected, L"drive is set as the current drive.");
            switch (newDriveSelection) {
                case 0:
                    SetWindowText(newdrv, L"The C: drive will be when you click Apply.");
                    break;
                case 1:
                    SetWindowText(newdrv, L"The D: drive will be when you click Apply.");
                    break;
                default:
                    SetWindowText(newdrv, L"");
                    break;
            }
            SendMessage(CDrvButton, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(DDrvButton, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(apply, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(quit, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(the, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(drive, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(selected, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(newdrv, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            EndPaint(hWnd, &ps);
        }
        break;
    case WM_DESTROY:
        DeleteObject(s_hFont);
            PostQuitMessage(0);
            break;
        default:
            return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

What could be causing the problem with my code? I think it's a problem with the WM_PAINT handler because this sometimes also happens when un-minimizing the program.

Window glitches after redrawing with RedrawWindow or SendMessage(WM_PAINT)