Welcome to Ecf. I love the cCell coils! I use them in a Melo 2 tank and have been for quite awhile now.
They do have a bit of break in time. I fill the tank after dripping about 10 drops directly into the coil. Then, I let the tank sit for about 15 minutes. I start out at 15 W and stay there for my first tank. Midway through the second tank, I move up to around 20W. By the third tank, I move up to 26W which is my sweet spot with these coils.
I have found that if you let the tank run fairly low on juice, it is very easy to change flavors. After just a few draws there will be no trace of the old flavor.
Also, I am able to "dry burn" these coils to clean once they start tasting "off". Once I use this method to clean them, they are like brand new again. I get several months from each coil.
I do hope that you find this info helpful. My guess is that you are either not letting the coil "soak" and get fully saturated for long enough on first fill or, you are not starting off low and moving up
Good luck because these coils really are amazing for vapor and flavor once you get them figured out
ETA- I do hope that you have saved the coils that you got the burnt taste from. They are very easy to recover after priming/breaking in correctly without even a hint of the burnt taste left behind.