treetable rows collapse after scroll up

Webix JS
1 
webix.ui({
 view: "button" ,
 value: "lol",
}).attachEvent("onItemClick", async () => {
	$$("tree").showItemByIndex(100);
})

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

Steps:

  1. click on check button
  2. open the highest visible row
  3. Scroll up

Opened row becomes closed. Expected behaviour is that row stays opened