This is an unexpected high pothesis. The area under the airpath filter screen and below the airpath glass pipe, could be called a resin recirculator or capture device. It is like the appendix in the digestive tract, there is the main flowpath and then a small area for material to collect.This might be due to the temp getting high enough in the bowl after 7min to partially vape some resin somewhere in the vape that may have been missed during cleaning.
The way it works is resin makes it's way there during use. Also, it condenses onto the glass pipe. When the air is hot, some of this condensed resin vaporizes, either on the glass airpipe or in the resin recirculator.