I don't know that quad, so I'm of limited usefulness. However, the first thing I would do it bring it briefly off the ground, then shut off the transmitter to see what it does on loss of signal. Ideally, it should land. Less ideally, it might just cut the motors entirely. I would be surprised if it simply continued to run without control signal, but it's possible. By checking you should be able to get a sense whether loss of signal is causing your issue.
If not, the next step would be to switch out of GPS mode if that's possible with that quad, and see if your problem still happens. If it does, you have eliminated loss of GPS signal integrity as your cause as well.
If you eliminate control signal loss and GPS signal loss, you would be left with a receiver or flight control board issue, and should contact the seller for a return.