Problem with a prity s 1 wood burner - HELP

Hi, does anyone have an s1 woodburner that they can help me with. Mine has been set up a few weeks, but the top air vent keeps falling out when I open the door. I can't seem to work out what I am doing wrong - it doesn't have a handle on it either so you have to open the door in order to adjust the vent and we didn't find any instructions of any sort for it when we bought it. Does anyone have any instructions that they could email or photos or video of how it is attached ? Thank you in advance for your help.

Hiya, I found this on the net It may be helpful, or not.
https://www.energy-economy.eu/en/stoves … 1-w10.html

Terry