I'm a bassoonist (not that great of one, but I can make pretty noise ) and I just discovered that when slurring from a low F# to low E natural, either I get a really loud key pop or if I manage to avoid it there's a really short F natural in between the notes. This is because there's this HUGE key that I call the pancake that directly covers a HUGE hole. Right next to it is a key that lifts a key further down the bassoon. Going from one to the other makes the pancake pop, or I have to lift the other key and go down to the pancake resulting in a tiny F natural.

So in conclusion (I feel like I'm writing a research paper here! ) try to avoid these slurs and if you're trying to simulate a beginner, stick in that F natural. I'm sure professionals have found a way around this artifact, but I (a somewhat beginner) have not found it.