NSE rarely has such problems. It's a serious problem and unfortunate, but at least NSE is keeping you informed to a certain degree. Zerodha faces problems much more frequently and then you're stuck in limbo not knowing where you went wrong in life (you chose Zerodha, that's where you went wrong). Zerodha's phones will be busy or simply not working, they won't respond to your emails, and if they do respond, it will be a blank email without any words causing you to wonder what the point of that email was which is literally blank. That's the Zerodha experience.
disclaimer: I sadly still use Zerodha, but have opened an account with another broker and will shift half my money to them