I bet the black text under the white text would give us a clue if we could find out what it said...
It says "Transition begins after 5 frames of black". This was determined by taking frames of the video with the X present and without the X present, and doing a subtraction, which left only those parts of the image that had changed. That clearly revealed the mystery message. The question is, then, is this a standard message that the equipment gives during routine operation, or was it added in by a malicious operator as a CYA to deflect blame away from himself and onto the equipment? I can't answer this, I am only speculating.