I keep seeing this error in my Developer Console each time I load a page or a Lighting Component in my Lighting App. Please note there are no LWC components in the app. I see my scratch org is a new Summer 19 org, it's possible something in my code is causing this or it's a problem that started with the new API release.
I apologize, but I don't believe posting code will be helpful as I can't pinpoint which Custom Lighting Component (if any), of the very large code base, is causing the issue.
What, generally, can be the cause of this type of error?