I'm more inclined to thank that the accumulated alcohol is left after still is shut down
Absolutely not. I had a marker on the glass thumper before the operation and observed the operation all the time. Here is what I observed in the thumper and how it was bubbling:
Since I have a thermometer at the top of the main column I see about three styles of bubbling:
a. while the temp in the boiler is rising to reach 165 degrees f, big bubbles come into the thumper with breaks in the intervals
b. once the temp indicates 170 to 180 degrees f, the bubbles change form into small and rapid discharge from the pipe, this is where the accumulation of liquid is happening.
c. maintains the temp 178 to 185, I adjust the temperature to the boiler, lower it a bit and once the system is going, you can bubbling where the water in the thumper is being thrashed around. This the stage that I start getting distillate and continues on till my ABV% output drops.