All right. It's based on the volume. If you look at the outstanding shares, which is updated at least monthly, and you watch how many shares are traded during the month you can kind of get a clue on when a drop is about to happen. Going to have to use some math to keep track. When a stock is running out of shares to be traded the pressure on the price is less. People are holding, less shares available means sell. Drop is imminent.
And in the case of Meta, that's probably what was going on. Seems to happen a lot leading up to earnings calls or whatever.
Sometimes it could be the news though.