When an actual price change occurs bitstamp volume is tiny. But when nothing is happening suddenly people "trade" thousands of Bitcoins back and forth with no price movement whatsover.
What also happens is that whale traders want to increase their total generated volume for the month to get lower fees in return. This mostly happens when there isn't volume. That makes it easy for them to put up a large buy wall and dump in their own buy wall a second later to prevent others from buying up their coins.
unlikely especially considering there isnt much "real" liquidity on that exchange anymore.
You ought to take a look at what Bobby Lee CEO of BTCChina says about these kinds of things way back in early 2014 (hint: nothing has changed).
Bobby Lee on exchange volume deception:
https://www.youtube.com/watch?v=2M12zzwNkCo&t=12m35s