If you select multiple cards and toggle suspend, it will toggle all the cards based on he state of the last selected card. So if the last selected card is suspended, selected cards that were all ready suspended will remain suspended non suspended cards will be suspended.
However, if the group of selected cards contains buried cards, and the last selected card is suspended, unsuspending the group of cards will also unbury all the cards. Toggling suspend should not also toggle bury.
To recreate error:
Select 3 cards in this order: an unsuspended, a buried, and a suspended. Then press the suspend toggle shortcut. Notice the suspended card is now unsuspended, but the buried card is also unburied
Additionally, suspending then unsuspending a buried card also unburies it. I think the suspended/unsuspended state should be a layer on top of the buried/unburied state.
i.e a card should be able to be both buried and suspended, in which case the suspension will take priority
This is a known limitation, and not easily solvable, as it is due to the way Anki stores card states.
A card cannot be buried and suspended at the same time. Suspending a buried card will unbury it. Burying a suspended card does not work on Anki 2.1.49+, whereas on earlier versions, it will unsuspend the card.