When the Emergency Stop Button is pressed my Wanhao Duplicator 4 with Sailfish firmware doesn't stop, it starts advancing in the Y direction until it hits the front panel and motor continues trying to advance more.
In V4 all worked as it should.
Interesting. If you look at the Machine Control Panel Communication log, can you see what command gets sent in V4 when you push the emergency stop button? Is that same command sent from V5?
Maybe you can post the communication log from both versions in this thread so we can see them.
Version 5.0.1 was just released with improved behavior for the emergency stop button. It should work better on a wider variety of machines now, including your Duplicator 4.