We've seen this issue on our SCA site before (Anconcagua R2 v2018.1) but over the last couple of weeks, we've had days where the problem is much more prevalent. Occasionally we'll have periods of time where our extensions all fail to load on the site. Typically this is on your first visit to the site in your browser session and typically a simple page refresh (after the page is loaded errantly) will cause extensions to come back, but not always. There are some very key pieces of functionality tied to our extensions so them not loading is a big deal.