I’m using proof grade materials, have the exhaust tube unobstructed, and running the machine like I always have, but more and more, I have to run a shop fan to blow out all the smoke that escapes from the machine.
Nothing appears to be wrong with the lid, but it smells like a health hazard in here.
While running a print, check to see if the air assist fan is blowing hard towards the front of the machine, and if the smoke is then being picked up on the left side and sucked out the rear. If not, one of the fans might need cleaning or service. (Likely the air assist fan.)
There should not be smoke coming from the lid. Check to make sure that your exhaust fan did not get toggled off. Click the three dots in the interface. If you don’t have an inline fan, the air filter toggle should be off.
I agree with @Jules and this sounds like a classic example of the fan needing cleaning. (Especially the part about the issue getting slowly worse.) When was the last time you cleaned the rear exhaust fan?
Good luck! Let us know how it goes and if you get it cleared up. And FWIW, you’re in good company as this was a comment from me in 2017 when I and a few others experienced this exact same issue and didn’t know why. This was when GF was first released, and some didn’t realize how important a clean fan is for removing the smoke.