Consistent Sales Drop Around Amazon Payout Days — Is This Normal?

I've been selling on Amazon for a couple of years, and I've noticed that my sales always drop on or a day before my payout date — every single time. Since my payouts are biweekly and the payout day keeps changing, it doesn’t appear to be tied to any specific day of the week. I also keep my advertising budget consistent during that time — and sometimes even increase it — but it doesn’t seem to make a difference. In fact, it feels like the ad spend goes to waste during those periods. Is this a normal phenomenon? Have other sellers experienced the same pattern?