An old price is no longer sent after a newer one

When an older price change was still unconfirmed and a newer one had gone out in the last two hours, the Repricer could send the older one again, reverting its own change. If one of your prices went back to an older value on its own, this was probably why. When it sends an unconfirmed price again, the Repricer now always takes the listing's newest price change, and one older than a day is never sent. How a price is confirmed and re-sent is described in What Repricer writes.