It's best to pre-fill the carto & let it sit before the first use. Did you get the same resistance carto? Lower resistance burn easier. Freshly charged batteries are hotter & can result in a burnt taste.
How long should it sit for after pre-filling? I let the second one sit for about an hour, and it too is nasty and burnt. I have another sitting filled, from another package. Both I tried so far were from the same 2-pack package. I've emailed Vapage to see what they say. Don't want to burn through any more of these if I am doing something wrong.