I day trade ETH every day and for three days last week, I watched this buy wall constantly appear, disappear, and reappear. At incredible speed too, so I figured it must be a bot. It was a buy order for roughly 300-400 ETH each time. It would appear about $4-5 below current price. If current price got within $2-3 of this buy order triggering, the buy order would immediately disappear. Within a 1-2 seconds, it would reappear at lower price again at $4-5 below current. This went on for three days straight, all day and all night. The moment it stopped, the price dropped off about $40+ before stabilizing.
A VERY old trick in the futures market is to place a large fake order near an important price point (the market tends to gravitate toward a that target and tends to hit it when market participants know that there is a large order just beyond it) and then cancel the large order when it comes close.