What would cause the price of Bitcoin to flatline for several hours on Bitstamp?

Question

Last night I observed the following flatline of BTC/USD prices for several hours on Bitstamp:

What would cause this ?

Answer 1

I think this was "Bitcoin Sell Wall of Death" at Bitstamp. Somebody sold 31 000 BTC at 300 USD. The wall was eaten over Sunday-Monday night.

https://www.cryptocoinsnews.com/bitcoin-sell-wall-death-chomped/