I've never had this experience. You did not mention what device you are putting the coils in or what the wicks are made from, which would have been very helpful to know. IMO it may be that there is still some oil residue left or a bit of burnt oil residue. I would try burning a bit longer to attempt to get rid of it all.
Also, taste can be very tricky. Are you sure this is from oil? If your coil has a short you will taste burnt
juice which you might be interpreting as coming from oil. I use Gennys with SS mesh wicks. I always make sure to pulse the shorts out of my coils before putting
juice on them. Even after that the coil will typically short once more in the next day or two before it settles down.