starting line~ and trying to synchronize count~ at the same sample-accurate time, all using bang and messages, will not be sample-accurate enough, so something like this might be better for getting the exact waveform synchronized properly to start and end of buffer~:

hope it helps 🍻 (edit: there's also ways to have it automatically stop selector~ at the end of the count~(hint: you can control selector~ with signals too), but i'm a little tired and hazy from drinking lots of sake tonight, so i'll leave that for someone else to try... kanpai 🍶)

I would use gen if I were you. The code becomes more comprehensible in my opinion as well:

the other alternative is peek~

also, the signals of the signal objects connected to the bang will only be in sync when overdrive is on - and then you should add a [del 0] behind the button.