1st section of Chimney pipe fall down into the stove.Switching the position with the second pipe and the first may solve the problem

I would disassemble the chimney first to make sure everything is fine there. Next I would make sure the stove is getting good ventilation through the main chamber and the ash tray (sorry if I'm not using the proper nomenclature). Finally, I'd stick my hand in the stove itself to see if anything is lodged in the part of the stove that goes to the chimney from the main chamber and from the stove to the chimney.

Have you received any further help with this ? mine just started doing this same thing .

Have you checked the inside to see if anything is stuck or possibly stuck in the chimney?