ro-li

The following custom CSS did repair the problem:

@media only screen and (max-width: 640px), only screen and (max-device-width: 640px) {
  .sidebar > ul > li {
    min-width: 100% !important;
    display: inline-block;
    vertical-align: text-top;
    max-width: 100% !important;
  }
}