I think i have the same issue. I am using the SMOK Alien 220 with the TfV8 which i bought primarily for the RBA deck. I started with the prebuilt Quad coil which was great for the first week and then it got harsh and flavourless. I estimated that maybe the coil maybe only lasted a week and so i decided to give the RBA a whirl. Again this worked good for a day or two before the same thing happened. I have changed the coils, recottened several times, different juice, varied airflow and now set the mod to 'normal' but still no luck. I found when i started i vaped at 60W but since the problems started occuring, i have tried higher and lower.
It has got to the point where i may have to consider retiring the RBA deck which i am gutted about as i had really high hopes for this tank. I will probably try the Octuplet coil next but dont really want to stay on those coils as they are kind of pricey.
I also have a baby best which is definately the best tank i have owned and still is. My last was a Gemini RBA which also was pretty good.
Any insights would help to SAVE THE CLOUD BEAST!