PowerBI Embedded Export function works sometimes and sometimes not

I´m using PowerBI Embedded sample app  (app owns data) 

And my export function works sometimes and sometimes not.. There is no way of trouble shooting the issue as it starts working after couple of minutes even if I dont do anything.

My export function:

function exp() {
        report.getPages()
            .then(function (pages) {
                pages[0].getVisuals().then(visuals => {
                    console.log(visuals.length);
                    if (visuals.length >= 5) {
                        visuals[4].exportData(1, 1000)
                            .then(data => {
                                console.log('exportFunction');
                            })
                            .catch(function (errors) {
                                console.log('export error');
                                console.log(errors);
                            });
                    } else {
                        console.log("Error getting visual data");
                    }
                });
            });
    }

this code gives me error on line : visuals[4].exportData(1, 1000)  and gives me these errors (Sometimes): 

• reportembed.externals.bundle.min.js:646 TypeError: Cannot read property 'Underlying' of undefined
      at r.<anonymous> (reportembed.bundle.min.js:22)
      at a (reportembed.common.bundle.min.js:16)
      at Object.next (reportembed.common.bundle.min.js:16)
      at n (reportembed.common.bundle.min.js:16)
      at reportembed.externals.bundle.min.js:659
      at m.$digest (reportembed.externals.bundle.min.js:670)
      at reportembed.externals.bundle.min.js:673
      at e (reportembed.externals.bundle.min.js:570)
      at reportembed.externals.bundle.min.js:573
      at t.invokeTask (reportEmbed.min.js:1)

• reportEmbed.min.js:1 Unhandled Promise rejection: Cannot read property 'Underlying' of undefined ; Zone: <root> ; Task: Promise.then ; Value: TypeError: Cannot read property 'Underlying' of undefined
      at r.<anonymous> (reportembed.bundle.min.js:22)
      at a (reportembed.common.bundle.min.js:16)
      at Object.next (reportembed.common.bundle.min.js:16)
      at n (reportembed.common.bundle.min.js:16)
      at reportembed.externals.bundle.min.js:659
      at m.$digest (reportembed.externals.bundle.min.js:670)
      at reportembed.externals.bundle.min.js:673
      at e (reportembed.externals.bundle.min.js:570)
      at reportembed.externals.bundle.min.js:573
      at t.invokeTask (reportEmbed.min.js:1) TypeError: Cannot read property 'Underlying' of undefined
      at r.<anonymous> (https://app.powerbi.com/13.0.4898.154/scripts/reportembed.bundle.min.js:22:454)
      at a (https://app.powerbi.com/13.0.4898.154/scripts/reportembed.common.bundle.min.js:16:27283)
      at Object.next (https://app.powerbi.com/13.0.4898.154/scripts/reportembed.common.bundle.min.js:16:26618)
      at n (https://app.powerbi.com/13.0.4898.154/scripts/reportembed.common.bundle.min.js:16:26350)
      at https://app.powerbi.com/13.0.4898.154/scripts/reportembed.externals.bundle.min.js:659:168
      at m.$digest (https://app.powerbi.com/13.0.4898.154/scripts/reportembed.externals.bundle.min.js:670:130)
      at https://app.powerbi.com/13.0.4898.154/scripts/reportembed.externals.bundle.min.js:673:157
      at e (https://app.powerbi.com/13.0.4898.154/scripts/reportembed.externals.bundle.min.js:570:449)
      at https://app.powerbi.com/13.0.4898.154/scripts/reportembed.externals.bundle.min.js:573:300
      at t.invokeTask (https://app.powerbi.com/13.0.4898.154/scripts/reportEmbed.min.js:1:376613)

any idea of what is happening?