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.

[LenOlyott3]

Hi, I am seeing the exact same symptoms on a EXB 1.18 developer edition. What I have found is that the layer in my webmap that is being referenced is a secured WMTS. Now I have created an item for the WMTS and shared to my org but it seems that ExB is not liking the WMTS. Perhaps its an issue with WMTS as a whole. I have tried adding the tile API that the WMTS references but then it does not show in the print. The layer is an imagery layer from Nearmap for Australia.

ExB is apparently more GPU intensive than WebAppBuilder and there are whole threads on this. Basically it is to do with WebGL from what I can gather. However, this is a very specific issue I am seeing on this build with customers complaining about slow load times and printing simply failing. I look forward to answer around this.