How long have you had your glowforge?
Initially I had the same problem. I have an extended exhaust run, and carefully inspecting it including the booster fan, I found I had a lot of leaks. Every joint in the standard 4" metal vent pipe, especially the adjustable elbows had to be sealed. I used caulk. Took me about a month of sealing this or that joint. After I broke down and sealed everything I have zero smell. Only a whiff when I opened the lid.
After about 3 months of heavy everyday use I started getting smoke in the room, so like you I taped up the cracks. Turns out the exhaust fan guard was blocked by ash (If you pull off the hose and look inside you can see it) so the intake fans were pressurizing the machine so it was blowing smoke out of every crack. Cleaning the grill solved it.
Keep after it, you should be able to get the smell under control.