Data is loaded after Fullcalendar ends

I’m using fullcalendar to create an agenda with teachers’ classes, but when entering the schedule screen the data does not appear (even though it was loaded in the request). When I change the week the data appears, but it is all at the end, after the calendar. Anyone knows why?

`items: [{region: 'center',xtype: 'panel',html: '<div id="calendar"></div>',listeners: {render: function() {var calendarEl = document.getElementById('calendar');
            var calendar = new FullCalendar.Calendar(calendarEl, {               plugins: ['bootstrap', 'interaction', 'dayGrid', 'timeGrid'],               locale: 'pt-br',               themeSystem: 'standard',               titleFormat: { year: 'numeric', month: 'numeric' },               header: {                 left: 'prev,next today',                 center: 'title',                 right: 'timeGridWeek,timeGridDay'               },               dayMaxEvents: true,               margin: '10',               contentHeight: '550',               defaultView: 'timeGridWeek',               slotDuration: '00:15:00',                   slotLabelInterval: '00:15:00',                allDaySlot: false,                   showNonCurrentDates: false,               minTime: '07:00:00',               maxTime: '18:00:00',               firstDay: 1,               events: function (info, successCallback, failureCallback) {                 Ext.Ajax.request({                     url: sUrlContabil('public') + '?func=buscaGradeProf',                     method: 'POST',                     params: {                         codUnidade: codUnidade,                         codProf: codOrigem,                         ano: nbAno.getValue(),                         inicio: dtObsInicio.getValue(),                         fim: dtObsFim.getValue()                     },                     success: function (response) {                         var dados = Ext.decode(response.responseText);                       let events = [];                                              console.log(response.responseText);                                    dados.results.forEach(function (grade) {                         // Partes do horário de início e fim                         let startTimeParts = grade.HORA.trim().split(':');                           let endTimeParts = grade.HORAFIM.trim().split(' ')[1].split(':');                           for (let dia = 1; dia <= 7; dia++) {                             if (grade[dia]) {                                 let title = grade[dia].replace(/<brs*/?>/g, '').trim();                                  let eventStart = adjustDateToDayOfWeek(new Date(info.start), dia);                                 let eventEnd = new Date(eventStart);                                  eventStart.setHours(parseInt(startTimeParts[0]), parseInt(startTimeParts[1]), 0);                                 eventEnd.setHours(parseInt(endTimeParts[0]), parseInt(endTimeParts[1]), 0);                                if (eventStart >= info.start && eventEnd <= info.end) {                                 events.push({                                   title: title,                                   start: eventStart.toISOString(),                                   end: eventEnd.toISOString(),                                   color: grade[`COR_${dia}`] || '#FFA500',                                   allDay: false                                 });                               }                               console.log('eventos:',eventStart, eventEnd);                               console.log("Event Start:", eventStart.toISOString());                               console.log("Event End:", eventEnd.toISOString());                              }                         }                         });                                      successCallback(events);                     },                     error: function() {                         failureCallback();                       }                 });             }                             });             calendar.render();         }     } }
],`
Data format:"HORA_DATA":"2024-01-26 07:00:00""HORAFIM":"2024-01-26 08:00:00""DATAINI":"01/02/2024""DATAFIM":"20/12/2024"

I already tried to first load the events and then call the calendar, but it didn’t work, the screen was blank.