This situation is called a "runaway stove" and can be quite dangerous. From the pictures you have posted, it appears that this has been an issue for some time now.
First things first: The Vermont Casting Encore is a fabulous stove that can be quite efficient and heats very well! However, due to the nature of the construction, it does require a bit of maintenance. It is a cast stove and must be 're-built' from time to time. This is dependent on how often it is used; if it is overtired; burning unseasoned wood; etc.
When these cast stoves are overtired, the joints may be compromised and will permit high volumes of air to enter the fire box. This lends itself to free-burning. The hotter the fire becomes…. The more air it draws. THe more air it draws, the hotter is gets and so-on and so-on. This is dangerous. Because it is getting air from the spaces in the joints of the stove, adjust and even closing the air feed control, will do little to stop it. Additionally, you may want to be certain to replace the feed door seals at least every other season, if not every season. I would recommend a complete rebuild. It is not a difficult process to DIY. Or, you may want to call a local shop to have them do it. Again…It is not too difficult.
From the pictures that you have posted, it appears that the fire back is cracked / broken. This, in and of itself will not permit a re-burn and will cause the stove to be severely inefficient. This need to be replaced.
Let me reiterate… This is a 'high-end' stove. Not a cheaply made stove and should last a lifetime. The Vermont Casting Stove Company has made this stove for many many years and many homes have been heated with them. Great stove. But, they do need rebuilt every so often.
Hope this helps.