Hmm... I'm assuming you've used this juice before without the burnt taste, correct?
There could be a myriad of things that might cause this symptom, but the most likely would be subjective taste changes. It's entirely possible that you've "burnt" yourself out on this flavor and just need to take a break from it for a few days. Everybody has all day flavors, but most of us need to alternate once in a while to give our tastebuds a break from the constant
vaping of one flavor.
The burnt taste comes from dry batting, but a proper fill & spin should alleviate that.
Have you used this specific bottle of juice before with acceptable results? It might be a slight change in taste if this is a new bottle you just cracked open..