There was , there is and there will always be institutional manipulation of Bitcoin prices. because bitcoins are in very limited hands. in my opinion Mining pools , exchanges , and big investors are beside bitcoin manipulation.
I think there is, because this involves large transactions involving many people, most likely that there is a system that can manipulate the price of bitcoin, because everything happens online and anonymously. Who can ensure the truth of an information or data that includes prices or transactions is not a hacker? Because price manipulation occurs from time to time, it can cause sales / purchases desired by hackers.