They have shut down numerous times when there is large (usually downward trending) volatility. It is very suspicious. This has been happening for years now.
And yet there's nothing you can do about it unless you can prove they did it for personal gain; they operate a service outside the requirements given to e.g. the NYSE, and you the consumer agree to that risk by giving them your money.
So long as they don't actively mess with customer owned BTC (as in: only stall transaction orders, not outright take them away if that is even possible) I would not even be sure that provable personal gains would be courtroom material. (At least for and user vs exchange company, not for exchange company vs employee)