Like for example maybe there an oring on the tank that is damaged or lost during dissasemble for cleaning of the tank and now doesnt seal properly ….and it may not leak juice out but it may make the juice run freely to the coil more than it should…
Also could from bad use like for example vaping in very lower wattages but in your case it seems u dont do this mistake cause its not your first time vaping this atomizer…but just saying
I believe in your case u just got a bad coil…since i think u say it happend only with this new coil….
Happens often that some coils are bad even if they are bad new and may leak juice or flood or even have spitback and dry hits….
I would make sure all my orings and everything are in place and nothing got damage or lost and i would use a different coil unfortunately….