The sensor data is a reliable low-entropy indicator. The engines are probably cutoff based on the same data (most probably a set of load sensors on the legs). If the data indicates that the engine has cutoff, the craft is stationary and if the data is still streaming, then it's a pretty good indicator that it worked as expected. I would trust it more than the video - especially when the video is lagging heavily.
PS: I have worked extensively on something related. Video is good to have and helps in post-flight analysis. However, it can also mislead sometimes. Sensor data gives you a much clearer initial picture.