It's limitation of PowerShell ISE. Any application that will try to control the console pane will fail and/or get stuck.
Some of those commands are already "blacklisted", you can see those in $psUnsupportedConsoleApplications
.
Error you see is probably not relevant at all: ssh writes information to stderr, and PowerShell generates error on top of this message.
But it's the fact that ssh needs full control over console you are running it in (e.g. to enable you to run things like vim) that's "freezes" ISE. To see the same issue with built in applications you can try the same with netsh:
$psUnsupportedConsoleApplications.Remove('netsh') netsh
This should lock ISE as well, for the same reasons ssh is locking it.
BTW: if you want just run a few commands, plink.exe can be better tool than "normal" ssh. It works just fine in ISE, because it's not trying to take over console.