I get the Drop beeps all the time but the "Are you still here" beeps (346*?HT) only go off 50% of the time.

From the manual:
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There are three separate safety points programmed into the KN-8828B:
1) If the KN-8828B-2 displays a temperature of 356 F (180 C) within the first 8:30 of roasting time, the unit will alert you with warning beeps. If you do not press a button (other than EJECT) within 20 seconds, the beans will be automatically ejected. Pressing a button continues the roast as programmed.
2) When the KN-8828B displays a temperature of 410 F (210 C), the roaster will again alert you with warning beeps. If you do not press a button (other than EJECT) within 20 seconds, the beans will be automatically ejected. Pressing a button continues the roast as programmed.
3) When the KN-8828B displays a temperature of 428 F (220 C), the beans will be immediately ejected. There is no override for this safety function.
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In addition, there are also the "add beans" and "End of Cooling Cycle" beeping

Depending on how you roast and to what level, it is possible that the three warning beeps will not sound. If the Add and Cool beeps do not happen then there is something wrong with the alarm. You could wire an LED into the circuit, or talk to Michael at Hottop USA about a replacement.

Not having the Add and Cool beeps is not a problem, but missing the number 1 or 2 warnings from inattention will result in an incomplete roast when the beans automatically eject.

Those beeps are loud. I was wondering if there was a way I could turn them down. I sit on top of my roaster the whole time anyway.

When I was in LA I roasted outside, and the "ok I'm done now" beeps went off. I heard a guy next door scream "F****** ALARM!!!". It was 10am on a Saturday. I guess he had been up all night.