Independently confirmed. If machine is in "Depoloyed" state, you can mark it broken, then mark it fixed. The next time you choose the "Take action" menu, the menu will not present "Mark broken" for that machine. If you select all deployed machines, the count for "Mark broken" will be one less, excluding that one machine. If you attempt to mark all deployed machines broken at this point, MAAS will refuse, asking you to update your selection as "1 machine cannot be marked broken" -- but it doesn't tell you which one, it's now a guessing game.
Independently confirmed. If machine is in "Depoloyed" state, you can mark it broken, then mark it fixed. The next time you choose the "Take action" menu, the menu will not present "Mark broken" for that machine. If you select all deployed machines, the count for "Mark broken" will be one less, excluding that one machine. If you attempt to mark all deployed machines broken at this point, MAAS will refuse, asking you to update your selection as "1 machine cannot be marked broken" -- but it doesn't tell you which one, it's now a guessing game.