The thing that's undefined is a symptom of the real root cause - something's making loading the view take longer than the hardcoded timeout, so the Java part of the designer is 'giving up' waiting for the Javascript portion of the designer. The end result is the 'View config is undefined' error message, and a bunch of unrelated React errors because the page is in a weird, half-loaded state.
Contact support, and they'll see what can be done.