Long, long time ago I asked a similar question of a broker. His reply was, "It's just the market," meaning it's hard to know what's behind each trade.

Not that the following is the whole answer, but here are a couple of thoughts. Say someone want's to sell 20,200 shares, without restrictions on the size of the lot or lots. Then say one, two, or three buyers take out all but 200 shares. Those 200 shares will sit on the market until someone takes them out, maybe a market maker (MM) to round out an earlier order, say, for 1,000 shares that "tick" by at 200 and 800 shares.

This can work the other way around too. Someone wants to buy 20,200 shares from all the cash they have on hand, but the broker can only find 20,000 at that moment. So, they might buy 20,000, and look for the other 200 to be filled later in the session. I've watched the ticker as some of my own buys and sells worked this way.

My point is, manipulation and/or conspiracy do not have to be behind everything that looks odd in the market. "It's just the market."