no it isn't normal
trane has a method that seems to work well to solve this
special cleaner that is sprayed on the Eva coil while the blower is on and let to dry and done again just for good measure the a trane stay-cleen coating is sprayed on the coil with the blower on and let to dry and sprayed on a second time
have done this a few time and seems to work well
also recommend a UV light between the coil and the blower as to help kill any bacteria growth and prevent the odor from coming back next year