Treetable closes opened row after scrolling up

Webix JS
1 
webix.ui({
	view: "button",
  	value: "check",
    click: function(...args) {
    	$$("tree").showItemByIndex(100);
  }
});

webix.ui({
  id: "tree",
  view:"treetable",
  columns:[
    { id:"value", header:"value", template:"{common.treetable()} #value#",width:300}
  ],
  url: {
    $proxy: true,
    load: function(args, options) {
      	console.log(options); 
        let start = options?.start ?? 1; 
        // start += 1;
        console.log((options?.count ?? args.config.datafetch))
      	const res = []; 
      	for (let i = 0; i < (options?.count ?? args.config.datafetch); ++i) {
            let parentId = start + i; 
        	res.push({
                id: `${start+i}`, value: "vals", "open": false,
                "data": [
                    {
                    	id: `${parentId}_1`, 
                    	value: "child",
 
                    },
                    {
                    	id: `${parentId}_2`, 
                    	value: "child",
                    }  
                ] 
            }); 
        };
    	let fin =  { data:res, parent: options?.parent, total_count: 200, pos: options?.start - 1 };
  		return fin;
  	},
    save : function(args) {}
  }, 
  datafetch:2
});

Steps to reproduce:

  1. Click on the button
  2. open the highest row
  3. Scroll up

After scrolling up opened row will be closed. Expected behaviour is that it remains open