searchPanes cascadePanes with serverSide cascades only after manual refresh

Hello,

See table config below:

$(document).ready(function()
{
  /* non debug url */
  url = '/'

  count_accept = 0;
  count_reject = 0;
  var thetable = $('#thetable').DataTable({
    "dom": 'Pfrtip',
    "order": [[0, 'desc']],
    "processing": true,
    "serverSide": true,
    "searchPanes": {
      "cascadePanes": true
    },
    "ajax": {
      "url": url + "get",
      "type": "POST",
      "dataType": "json",
      "dataSrc": "data"
    },
    columns: [
      { "title": "Date", "data": "_authdate" },
      { "title": "Result", "data": "_reply" },
      { "title": "Username", "data": "_username" },
      { "title": "Client MAC", "data": "_callingstationid" },
      //{ "title": "Switch MAC", "data": 5 },
      { "title": "SSID", "data": "_calledstationssid" },
      { "title": "Switch Port", "data": "_nasportid" },
      { "title": "Switch / AP", "data": "_nasidentifier" },
      { "title": "Connection", "data": "_nasporttype" },
      { "title": "Switch / AP IP", "data": "_nasipaddress" }
    ]
  });

Search panes function works great, in that I can select filters and have the table update. The backend is implemented in python/flask, similar to: https://gist.github.com/LexPanov/8cb89c6515946fa0def2147656ed9ed9

However, the panes do not cascade. I have a refresh button that does the following:

  /* refresh button */
  $("#refresh_button").bind("click", function()
  {
    thetable.ajax.reload();
    thetable.searchPanes.rebuildPane(undefined, true);
  });

When clicking the button, the search panes are cascaded and each item counter is updated correctly, reflecting the selected filters.

Is there something I should be doing (either client or server side), to ensure that the panes cascade and update their values correctly, when a filter is selected?

Apologies I am not able to provide a test case in this instance, as I was unsure how to replicate the server side facility with search panes, in order to effectively demonstrate the problem.

Thanks in advance