Experience builder application slow load time at the Beginning

[GISFunctionalGroup]

Hi Everyone,
Recently we've deployed an application which is built on ExB Dev 1.17V with ArcGIS Enterprise 11.3v. we have configured for all 3 devices (desktop,tab & mobile) and deployed to the IIS. 

First time when user opened the ExB application it's relatively very slowly loading and giving the following warning in the browser developer console. The below warnings are around 60-70 in the console might be giving slow performance of the application.

"index.js:2 Create data source error. dataSource_1-199517f846e-layer-9-0 h: data source id: dataSource_1-199517f846e-layer-9-0, Create error outside createDataSource method."

Is this the general the performances are slow w.r.t ExB (when compared to the WAB). @OliverIshmael  - You have faced the same performance issue with AGOL does it resolved?? If it's resolved kindly provide your comments please.
Can anyone explain/ provide the root cause of the slowness of the application. 

Thanks in advance.

[OliverIshmael]

Unfortunately not. We are currently waiting for our IT department to upgrade our systems to Enterprise 11.5, which we believe will improve the performance.

[GISFunctionalGroup]

Thanks for the reply @OliverIshmael . Hope someone would provide suggestion to improve the performance of the ExB app.

[TimWestern]

Out of curiosity, how many layers are being used by the experience?   Are they all on the same Enterprise setup? are any external?  I know when you have a large number of these, not just layers within a map, it can sometimes take a bit of time to load it. because of the simple number of asynchronous calls the app has to make.

I can't remember, if some of the widgets may have lazy loading options, but I have seen this with at least one example I've had to work with.