You don’t mention what OS you’re using, but keep in mind that the ServerManager cmdlets in 2012+ use a certain amount of Remoting under the hood to do their job. That could be causing the hangup, possibly with a credential problem. It’s also possible there’s some interaction between WinForms and Write-Progress; you could try setting $ProgressPreference to SilentlyContinue to test that theory.
We’re not seeing a ton of folks trying to build GUIs around PowerShell tasks, which is one reason you’re probably not seeing people answer that other question.
Can you help me understand the larger task you’re trying to complete? Maybe approaching this from a different direction might help. Do keep in mind that the whole WinForms thing isn’t PowerShell’s real “intended” use case, so it’s not uncommon for weird stuff to crop up.