I can't find much about this error code, it isn't in the docs.
All I can find is this GitHub issue https://github.com/angular/angular/issues/50742
Seems to be to do with angular not detecting zone.js has loaded.
That issue suggests that you ensure poly fills and runtime gets loaded before main.
I've done that, still getting the error every now and then.
Other problem is there's no easy way to reproduce it as 99% of the time it doesn't happen.
So has anyone else had this error code and if so how did you resolve it?