Here’s a video of the leak. I’ve done the usual, levelled the GF, cleaned the fan port, checked the seals. But it’s still pouring out smoke. I’ve tried a second in line fan, straightened the hose (it runs 5feet) I’m cutting 2mm MDF.https://youtu.be/VD_vyLz5bVs
I’ve got to stand outside to use the GF!
Not sure what to do next! Maybe get a gas mask!
So I assume you didn’t accidentally click the compact filter button under the gear icon? It sounded like a fan going, but video can be really hard to tell what noise is what, how loud, etc.
Can you remove the exhaust and take a picture of the fan port? You should be able to shine a light in there and see if the blades are all gunked up. If so, you may need to get the recommended degreaser spray and clean the fan. Otherwise, an obstruction downstream could also cause a build up of pressure forcing the GF to vent out of wherever it can.
No its set for external venting.
I’ve really only started using the GF recently although I’ve had it about 6months.
The port looks clean .
From what I saw, the laser head was near the right front corner (when it was pushing out smoke).
Couple of things,
How long is the exhaust tube and how many bends?
Was it breezy outside and when you open a door/window, do you get an inrush of air?
If you house is under negative pressure, the Glowforge venting is fighting that negative pressure.
Thanks for all your answers 
But I think I’ve found the culprit!
A blow back prevention gate at the exit point of the vent. I’ve remove the gate and it’s now allowing a greater flow of air. No more leaks.
Thanks again!
Yeah. You gotta rip those out. But I put a piece of wire mesh screen over the opening. Squirrels, it seems, are drawn to dark 4" openings in a wall. I heard one scrabbling in my hose, about a week after I installed the vent for my GF. Though in fairness to the squirrels, my vent is only about 12" off the ground. It’s both tempting and an easy target. Sans flap, the vent needed alternative remediation.
make sure that wire mesh is big. it will begin to collect char and eventually clog up if the holes aren’t big enough.
