But what about the buildup you can't see or smell?

My old canner manual said to always test with jars, but your water-only idea makes way more sense. I was ruining good beans every time a seal failed. Now I just do an empty run first, which saves a whole batch.

I mean idk, maybe it's just me but the "common sense" stuff is usually what we skip over. Those videos sound basic but I've had to relearn that being curious actually takes work when you're stressed at a job. Paying for it kinda forces you to take it seriously, a free pdf won't do that. The refund window thing sucks but the real problem might be expecting a magic trick instead of just practicing the simple advice.