Burn off cycles do not reveal any significant odor
Not herb below the screen then.
I also use 100% iso to clean the top of my Roffu oven, I have squirted iso through many vapes to clean them and just make sure to thoroughly force dry o/night before using them again. I have a Fury2 that blocks up from bong blowback that has had iso squirted through it more times than I can remember so I doubt iso has anything to do with your odor.
I use my Roffu in a few different ways and only get popcorn taste when the load is spent.
Below is an example picture of my use (no stir for any way I use it).
Native/OG, glass oven (no capsule, 6min @180c) for on-the-go with or without capsules depending on the situation...no capsules for better flavour and usually larger clouds simply due to extra herb fitting in the oven without the capsules.
WPA/glass mouthpiece (capsule, 2x6min @190c) mated with S/S oven for added conduction for that mouth-pull joint feel. This setup usually takes longer to get vapor but also takes longer finish (and the reason for the silicon sleeve, it gets hot) and can be more relaxing puffing on it than shifting a lot of air when chasing flavour/clouds convection style. The extra conduction results in a darker roast and more of a 'stoned' feeling for great pain relief.
Finally, (no capsule, 6min @180c) my favourite way to enjoy the Roffu is a glass oven attached directly to a j-hook so I can remove the vape/heat from the bowl between puffs. This gives me the cleanest flavour and is simple to load, empty and clean with a very even roast.
I will also add that my latest version of the Roffu (improvements/tweaks have been ongoing) which uses the stainless steel spring retainer for the oven had less smell during the burn-off-before-first-use smell.