I saw another post from someone else having the same issue. I'm using BigSSH node as a client and couldn't get a command to run. Being very tired when I got to this part of the flow I didn't catch the exception in time but today I did.
Answer: check for a handshake error with BigStatus node connected to the middle output of the BigSSH node. Hit the command and wait. Once the timeout hits, you should get the real reason why this connection failed. All other SSH nodes I've tried didn't produce much output at all.
Cause: In my case, my DiskStation's SSH cipher profile was set to High, which is likely failing to handshake with the default settings used by the Node. I lowered it to Medium just to verify and sure enough, a quick "pwd" command ran just fine.
For Node-RED / BigSSH developers: I found a strange behaviour in the TLS handshake fail scenario: Node-RED becomes unresponsive. Running in docker (latest official image) on a Raspberry Pi 3B+. I have to kill the container at this point, a simple "stop" or "restart" times out. No output in the container logs either.
I hope this helps someone.
