Re: error: the ethernet-switching subsystem is not responding to management requests

I believe, at least currently, ddos protection is only available on MX, T and EX9200 products:

https://www.juniper.net/documentation/en_US/junos15.1/topics/example/subscriber-management-ddos-example.html

You could maybe try reset a Junos OS process:

https://www.juniper.net/techpubs/en_US/junos15.1/topics/task/operational/junos-process-restarting.html

Now Ethernet-switching is not an option, but 'maybe' interface-control might work???  Otherwise I would perform a switch reboot/reset, and if issue remains, then maybe RMA the switch.

I do also assume you have a TAC case open.  Good luck.