Similar happened to me not so long ago. One day a junior admin asked me to diagnose who ssh to a box started hanging. After a bit of diagnosis it became evide

Similar happened to me not so long ago. One day a junior admin asked me to diagnose who ssh to a box started hanging. After a bit of diagnosis it became evident TCP's 3 way handshake got through, and then it all stopped. No normal network behaves like this. My answer was "some network admin is having fun with a middleware box", you will have to speak with them. They did, and the response that came back is "we are moving to a network with real security". Access was restored. It was a Palo Alto NGFW as others have mentioned. IMHO the industry looking for way to move high priced gear, and they convince someone with a sparrow problem with barely knows how to handle an air rifle to buy bazooka's. A bit of collateral damage is to be expected....