在Ext JS 6.5.3中得到这个错误，我怀疑它与这里定义的树存储有关：

Ext.define('Company.view.reports.AdvancedTripsReportViewModel', {
    extend: 'Ext.app.ViewModel',
    alias: 'viewmodel.advancedtripsreport',

    requires: [
        'Ext.data.Store',
        'Ext.data.TreeStore',
        'Company.model.AdvancedTripsReportRecord',
        'Company.model.AdvancedTripsReportTreeRecord'
    ],

    stores: {
        AdvancedTripsReportTreeGridStore: {
            type: 'tree',
            model: 'Company.model.AdvancedTripsReportTreeRecord',
            reader: {
                type: 'json',
                //root: 'Root'
            },
            rootVisible: false,
            storeId: 'advancedTripsReportTreeGridStore',
            remoteSort: true
        }

这里有一个在 Sencha 论坛中定义的bug，但不清楚它是否已经解决：https://forum.sencha.com/forum/showthread.php?468923-Race-Condition-in-TreeStore-setRoot