It happens after some time of resizing window. Browser view area will become only portion of the window with scrollbars being misplaced. Sometimes whole window will menu bar buttons and borders will become just white background.

Maybe this is upstream CEF Issue #1882.

There was new function CefBrowserHost::NotifyMoveOrResizeStarted() added in upstream CEF Issue #1208. In cefclient in RootWndProc there is this code:

case WM_MOVING:
    case WM_MOVE:
      browser->GetHost()->NotifyMoveOrResizeStarted();
      return 0;

I will add it and see if it helps. But looks like this is only for <select> and similar controls on a page.

Created a topic on CEF Forum in regards to NotifyMoveOrResizedStarted() usage: https://magpcss.org/ceforum/viewtopic.php?f=6&t=13885

Debugging in VS 2013 gave this FATAL:

[0212/205153:FATAL:hwnd_message_handler.cc(1867)] Failed to create DC in BeginPaint(). GLE = 1425, GDI object count: 10000, GDI peak count: 10001 

Reported on CEF Forum: https://magpcss.org/ceforum/viewtopic.php?f=6&t=13886&p=29628#p29628