Visual indicator that a maintenance is in progress

On the edit deployment screen, if you click Preview or Deploy against a computer, and that computer has a maintenance session currently in progress, the Preview or Deploy button will not do anything. You can click it a hundred times, with no visual indicator that it’s busy.

I do agree that a warning or some visual needs to be added when you are trying to Preview/Deploy something. It could be a pop-up letting you know that this won’t work until the deployment is finished. There are a number of ways they could accomplish this.

As far as the issue at hand, you can only have one deployment running on a device at a time. If you try to do it again, it won’t work until that task is finished.