I posted this as a comment on a closed thread, so I thought I'd post it here so people might actually see it.
I can be 100% certain that these were bad coils. I've had this problem repeatedly with the nautilus 1.6 coils. Most times its the entire 5 pack that is bad.
I know this because I buy ~100 coils at a time, and can swap different coils, brand new, guaranteed to be authentic, which are supposed to be the same... certain ones, brand new have that off, somewhat burnt, stale and headache inducing would be a better description.
I wasted around 10 coils to be sure of this, used different mods and different wattage/volts to be sure. I needed to be 100% sure there wasn't a difference.
Final nail in the coffin was when I opened up one from a 5 pack that had previously had ones that tasted off, and one from a pack that seemed normal. Both were primed identically, the nautilus filed with juice and let to sit for 2 hours. This was done on my two MVP 3s side by side, with the same 50PG/50VG high quality juice.
It should be said that these two 5 packs were purchased at the same time, are identical looking, and both 100% authentic.
After waiting the two hours, I tested the two identical set ups (at 11W on the MVP 3s), and sure enough the one that had other off tasting coils in the pack tasted completely different.
It's not so much a burnt taste, it's more a stale / putrid kind of taste. This was on two identical rigs, with identical set ups, same wattage, same juice, same everything.
This happened before about a year ago as well, at the time I put it down to what you are describing as the many different variables that could cause a burnt coil. So this time I wasted $30 in coils to be 100% sure it was the coils themselves that were bad.
My conclusion is that some batches of Nautilus coils are bad. I am completely certain of this. There are posts all over the Internet reporting similar issues, and aspire keeps saying it's user error. Which is why I felt compelled to test and post this.
It's unfortunate as the nautilus is my every day vape... and I spend a good amount of money on these coils.