1.8b6 Cannot mark a machine broken that is "deployed" and "on"

[Carla Berkers]

In 1.8b6, I

1. have a machine that is deployed and on

2. select that machine and choose "mark broken"

3. I get an error, saying "1 node cannot be marked broken. To proceed, update your selection. "

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I should be able to mark a node broken independently of its state
and the current error notification doesn't explain why the action cannot be performed.