Understood, and I’m sorry to hear it’s taken a while to get a response. As a community forum, we do our best to answer folks as quickly as possible but there isn’t an SLA like you’d get with Auth0 Support. I do appreciate you reaching out to me directly and hopefully we can get you back on track 
I understood that I’d to follow docs but how can I disable them like should I do it in my code? or I have to do it in Auth0 dashboard?
Auth0 extensibility is all run on the Auth0 platform, so you should be disabling it via the Auth0 Dashboard. You should not need to modify your code 
And what about that Screenshot? Did it helped you to understand problem?
It was helpful in supporting the current notion that the problem is related to some unhandled exception within custom extensibility. So let’s continue down that path for the moment. And if you also take a look at the Auth0 Logs (see here for details) you should see an error that corresponds to the server_error shown 