there are certainly people out there manipulating the markets for their own profit.
Isn't that the idea?
Market manipulation is tricky and rewarded economically. You have to assume that's going on in any currency, as painful as it makes it for those that need to rely on less volatility. Plan accordingly.
Yes, countries do this all the time. Japan manipulating the YEN by buying or selling massive amounts is a great and well known example. (other countries too of course)