This issue is fixable with the below patch. It can be included in a separate js file rather than modifying the original files.
$.paramquery.cHeader.prototype.createHeader=function(){var e=this.that,r=this,a=e.options,i=a.bootstrap,d=(i.on?i.thead:"")+" pq-grid-header-table ",n=a.ui,t=i.on?"":n.header,l=a.hwrap,s=e.pqpanes,p=parseInt(a.freezeCols),h=a.numberCell,o=e.colModel,c=a.sortModel,u=e.depth,q=a.virtualX,v=e.iGenerateView.colDef,f=e.initH,g=e.finalH,H=e.headerCells,w=e.$header_o;if(null==g)throw"finalH required for _createHeader";if(a.showHeader===!1)return void w.empty().css("display","none");w.css("display",""),d+=l?"pq-wrap ":"pq-no-wrap ";var _=["<table class='"+d+"' cellpadding=0 cellspacing=0 >"];if(u>=1){_.push("<tr class='pq-row-hidden'>"),h.show&&_.push("<td style='width:"+h.width+"px;' ></td>");for(var b=0,y=v.length;y>b;b++){var m=v[b],C=m.colIndx,x=m.column,j=x.outerWidth;_.push("<td style='width:"+j+"px;' pq-col-indx="+C+"></td>")}_.push("</tr>")}for(var M="pq-grid-col ",k=0;u>k;k++){_.push("<tr class='pq-grid-title-row'>"),0==k&&h.show&&_.push(["<th pq-col-indx='-1' class='pq-grid-number-col' rowspan='",u,"'>","<div class='pq-td-div'>",h.title?h.title:" ","</div></th>"].join(""));for(var C=0;g>=C;C++){if(f>C&&C>=p&&q&&(C=f,C>g))throw"initH>finalH";r.createHeaderCell(k,C,H,_,M,p,f,u,c)}_.push("</tr>")}e.ovCreateHeader(_,M),_.push("</table>");var z=_.join("");w.empty(),s.vH?w[0].innerHTML=["<span class='pq-grid-header pq-grid-header-left ",t,"'>","<div class='pq-grid-header-inner'>",z,"</div>","</span>","<span class='pq-grid-header ",t,"'>","<div class='pq-grid-header-inner'>",z,"</div>","</span>"].join(""):w[0].innerHTML=["<span class='pq-grid-header ",t,"'>","<div class='pq-grid-header-inner'>",z,"</div>","</span>"].join("");var I=e.$header=w.children(".pq-grid-header"),L=I.children(".pq-grid-header-inner");e.$tbl_header=L.children("table"),e.$header_left=$(I[0]),e.$header_left_inner=$(L[0]),s.vH&&(e.$header_right=$(I[1]),e.$header_right_inner=$(L[1])),I.click(function(e){return r._onHeaderClick(e)}),r._refreshResizeColumn(f,g,o),e._trigger("refreshHeader",null,null)};
But there are some other issues while show/hide columns along with grouping of columns, which are fixed only in v3.3.0 ( would be released in few days )