I am not sure it is resolved. If you have seen similar errors, and it happened to me, wouldn’t it be better to keep it as a bug, and make Nethserver more user friendly?
Maybe it’s a philosophy disagreement, but in my view the purpose of the Nethserver web interface is to make it accessible by non-computer geeks, in which case, as a long-term objective, the user shouldn’t ever have to clear the cache in their browser, or use a command shell to type in commands.
As an absolute minimum, the error message certainly isn’t user-friendly, as evidenced by the fact that you, the expert, so kindly had to intervene to tell me how to work-around the problem. But it doesn’t fix the underlying cause.