/* força o fullscreen do dcc.Loading acima de tudo */
.dash-loading.fullscreen {
  position: fixed !important;
  top: 0; left: 0; width: 100vw; height: 100vh;
  z-index: 3000 !important;  /* > 1400 do seu offcanvas2 */
}
.dash-loading.fullscreen .dash-loading-overlay {
  z-index: inherit !important;
}