[GTK] custom style sheet no longer works

My environment:
  Linux mint 18.2
  Gtk theme: Adwaita
  Gtk version: major = 3, minor = 18, macro = 9
  GLib version: major = 2, minor = 48, macro = 1
  WebKit2Gtk version: major = 2, minor = 14, macro = 2

1. First problem
My style sheet works properly for WebKit2Gtk 2.14.2:
void addMySheet(WebKitUserContentManager *UCM, const gchar *css)
{
  WebKitUserStyleSheet *mySheet = webkit_user_style_sheet_new (css,
          WEBKIT_USER_CONTENT_INJECT_ALL_FRAMES, WEBKIT_USER_STYLE_LEVEL_USER, NULL, NULL);
  webkit_user_content_manager_add_style_sheet(UCM, mySheet);
}
And the sheet are ignored in WebKit2Gtk 2.18.0-2.18.5
The style sheet content is very simple: #id {display:none}

2. Second problem (ok with 2.14.2!)
  My program executes some js script with alert statement. JS window is alerted.
  After that when I move the JS window with mouse I see renderning problem for window
  that is under JS window. Only after I close JS window the window is restored.