On IE11 I get "undefined" at the bottom of the page. Some intense debugging has narrowed it down to a Client Action called "InitECT" in Outsystems UI called by: LayoutReadyWeb (My Reactive Application) -> RunOnStart (Outsystems UI) -> ApplicationStart Web -> ECTCall -> InitECT

The issue seems to be caused by line 40:


On IE11, regardless of if the Application/Module has "App Feedback" enabled in /ECT_Provider/, it gives an undefined. My theory is that IE11 doesnt let you get .innerHTML of an XML element. Switching it to .textContent should be more compatible and appears to work fine.

That's correct Marcus. XML elements in IE have a non-standard xml property. An attempt to access  .innerHTML  on an XML element in IE will return undefined 

Good catch.