since it's the same IP address...
Same IP yes, but different services on different ports.
Lets say you spam incorrect work on scrypt pool -it may ban you for that, however x11 pool won't.
At least it may make some sense if anti-DDOS/hacking is implemented and nicehash does have something implemented.
It looks like their system is banning me for some reason at X11/X13 ports, I have tried another rig with a different IP, when I started it all pools were alive and after a while (without even switching to the X11 or X13 port) I have it both DEAD... Any idea what can be causing this?