No worries. I don't personally care for the smoked porter from the Alaskan brewery down in Juneau, but their Baltic Porter, in the years they don't pump it full of walnut/cherry/ pomegranite toro poopoo, is an excellent Baltic Porter. Their winter ale, with the spruce tips in it, is very very good, but more than two tonight will have you tasting turpentine tomorrow for most of the morning. I really enjoyed their now discontinued basic pale ale. Like may US brewers they are currently making stupidly bitter IPAs and customers are buying them. Their Kolsch is style correct with no significant flaws, the yeast they use on their amber gives me migraines. I basically keep an eye on the store shelves to see if they pumped any crud into the Baltic Porter this year. Should be out soon this year actually, thanks for the reminder.
At this point I pretty much have to defer to
@bholler , our local chimney expert. My sense of the thing is you have a local downdraft that is messing with your chimney function.
Your stove has a 5 inch collar, and you have a 5" uninsulated liner, 25-30 feet of it. If you put a reducer on the stove collar and put in a 6" liner, I don't know what that would or might do for you. Nor do I know what could go wrong.
I have seen several "special" cowls or chimney tops for tricky air flow situations, but I don't have experience with any of them.
I imagine you don't own the woodland beyond your back fence and cannot take down the 50 meters of trees closest to your home.
The only thing I can think of that you can do in the meantime is open the air controls to wide open for a few minutes (like 5-10 minutes) before opening the loading door. Go feed the cat or the dog. Go pee. Dance with your wife for three minutes. Ply your troth. Go make some tea. Then come back and open the loading door for a quick reload.
There was an article in The Guardian some months ago that comes up regularly when I internet search on terms like "wood stove indoor air quality." The particulates and VOCs they imply are found in UK homes are simply mind boggling to me. I am running two of the Dylos DC 1100pro and 4 more AQ meters with the plantower 5003 sensor. I simply cannot duplicate the AQ numbers implied by The Guardian without using tongs to stack a soccer ball sized lump of live coals on the hearth in front of my wood burner while reloading, and stopping for a cigarette during the reloading process, before shoveling the live coals back into my wood burner.
Besides visible light and palpable heat, burning wood, oxidizing wood, combining it with oxygen, emits fine particulates like PM2.5 and PM10 and some VOCs, Volatile Organic Compounds. Your DEFRA stove is supposed to deal with the particulates and VOCs with the door closed and blah blah, but if you open the loading door early you will get some bad actors into your living space even with good draft.
On the one hand, it is ideal to let the last load burn down to " a few embers" before reloading, but i have a day job. I also have a much deeper stove than yours, I can load wood 18" long in there, see the end grain of the wood and close the door. In reality, when I get up in the morning there is whatever left, I open up the air intakes, go pee, make some coffee, deal with the cat, and then open the loading door, get the reload over with, close the door and get on with my day. In regular weather I reload morning and evening. In cold (local) weather I reload morning, right away home from work and again at bedtime. When it is really cold I will get up in the middle of the night to reload the stove a fourth time daily.
What I am getting at is the new stoves aren't like the old ones. My grandpa (God rest his soul) taught me to open the loading door about every half hour and get in there with a stick of metal to stir things up and throw in whatever more wood would fit. With the old technology that worked good. Now that I have a modern stove, the hardest thing for me to learn to do was to leave the dang loading door closed until the current load was burnt down to embers, and then reload the whole thing all at once - and leave it alone until it is burnt down to a few coals again.
Look for how few coals do you need remaining for an easy reload. How far can you let the last load go and still get the next load lit off easily without smoking out the lounge? Don't forget to ply your troth with great regularity, it is one of the responsibilities and rewards of running your wood burner effectively. Just saying.