If this happens a few hours after a new filling, you need to add more drops to the top of cartomizer. Let's just say you didn't prime the cartomizer at all, it would take 37 drops to fill it.
At some point I think I am going to re-shoot or edit in the tank filling video and note the following for those experiencing a burnt carto after a fresh filling
If you are getting a burnt taste within hours of a fresh fill I would change the drops in the carto to 18 drops. Then I would note just prior to priming take notice of the juice level in the tank, prime it until the juice level drops by 1/8 of an inch.
While the instruction have worked for many, I think the variable is in the priming so adding 18 drops I believe will compensate for that.
If the cartomizer is not fully saturated after an initial fill it will prevent the self-feeding characteristics of the tank.