Bitcoin closed near $86,500 on September 21 and October 4, and a week later was more than 3% lower each time. Both times, short-term holders sent unusually large volumes to exchanges at a profit, including 30,100 BTC on September 21, the largest in a year. Two cases are a small sample, and transfers don't confirm sales. Still, the $86,000 area has twice drawn supply from recent buyers.