22 minutes in a popper! What size batch were you using? Were the beans moving on their own or did you have to stir? I cant recall popcorn noise too accurately but I can always clearly hear distinct first and second pops in a popper though some beans crack louder than others.
The last time I used mine (xu1 heat gun died this week mid roast *:( ) it wanted to hit first crack after 2-3 minutes. I have found light shaking to be useful in preventing to rapid a roast but thats not your problem.
Strongly suspect your popper is not operating in spec. 22 minutes straight at "normal" heat would also be very hard on the machine.