Have you checked one to see if maybe it's glue burning? any way to get pictures maybe?
I also mentioned a possible confusion about sying the words 'burnt taste' a long time ago.
(Lots of words have been used, chemical, plastic, burnt, glue, sealant, hairspray, burnt, dirt sock, dry, and each one could be a different problem)
Someone even thought they put 1ml in it, and it was only 0.1 ml
Have you dry burned a brand new one or an old one?
And what brand of juice would you be trying next? I hope you're not adding any water either, you mentioned some diy mixes too.
Is there gunk on the coil?
1. No glue that I can feel. I probably should have said a 'dry vape' taste rather than burnt.
2. Yeah, I remember that post about the 0.1ml. How embarrassment! I've tried them out with everything from 0.5ml to 1.6ml.
3. I've dry burned a used one that was a little gunked up, but most of them aren't blackened at all. As a matter of fact I thought at one stage the wick had come out of the coil completely as it was so clear (but it was still there).
4. Egads - no water ever.

That's what they invented Vodka for instead

I mainly use straight juices either 100%PG or 20%VG--80%PG. I only put a few drops of Vodka in for throat hit if needed. And even it has been used to clean out the syringe so it has traces of juice in it too.
I haven't taken photos yet as I don't know how to pull it apart. I'm also a little reluctant to sacrifice one as it took ages to get these. My last order from the US cost a minimum of $35 for shipping on a $200 order. It makes it tough to buy one or two packs of cartos to try so I tend to wait a bit and then order up big, including stuff I don't really need

But that's just the way it is here in Oz.
Of course, I will slaughter one for the cause, when I know how. I guess I'll need to learn how to post pics as well. The thought of learning two things in one day makes my head hurt
More to follow . . .