Yep, if there is not enough airflow, you will overheat the carts and cause them to burn out before their time.
Make sure that your battery is free from and juice residue that may have built up over time. Clean the threads with a paper towel and use a small/thin pin to clear out the air holes to increase the airflow.
If these are refilled carts, how many times have you refilled them? Because they are disposables, sooner or later, they will finally give out. If you refilled them a few times already, it's time to dump them.
Worst case scenario, have you tried other carts? If so and you have no problems with them AND the one's with the burnt taste are new, you probably got a bad batch. It happens sometimes and V4L will work with you on replacing a bad batch.