If it was venting OK before and then recently got really smokey, then @jbmanning5 is likley right and it’s usually a dirty fan. If it’s never vented well, then it’s probably a faulty fan or you don’t have it set up correctly. (FWIW, the hose that came with it works fine and you shouldn’t have to use a different one. ) Hopefully support chimes in soon and can help out.
This is perfectly normal and is not the problem at all. The GF doesn’t need to be airtight as the fan creates negative pressure. @PrintToLaser explained it well so there’s no reason for me to reinvent the wheel 
Well heck, I can never get the links to work well. Here’s what PrintToLaser had to say…
“You will only need to clean that fan grill after extended use, I had over 2,000 pieces engraved before it was needed. The exhaust creates negative pressure inside the machine, so any cracks like the lid or front door are pulling air in unless there is a restriction in the exhaust. Concentrate on sealing the duct connection to the machine. That duct is pressurized from the exhaust, so any cracks there are going to leak. With a sealed exhaust there is no smell except when you open the machine, or the residue on the work. A booster is a good idea, just mount it at the end, like right at the window.”