Has anyone experienced this issues before? DevTools failed to load SourceMap nlRUM.js failed to load Cannot read property 'isStandalone' of undefined

The first two you can ignore. As for the last, you'll need to be more specific from where that property error is coming from

It seems it comes from the Header.Menu.View and this.application would be undefined for some reason

OK, that's puzzling. I would recommend deactivating all of your extensions and see if it still returns the error. I would also doublecheck all your configurations to make sure they are correct (touch points, web site setup record, configuration file, etc)

I figured it out the extension was overwriting the intialize function of the source and was missing a few new lines of code.

OK, we would not recommend overwriting the properties of core classes for exactly this reason