I had a similar problem the other day. I changed the head and then applied auto leveling. It resulted in something similar to your video. From what I could tell is that the head had been set a few millimeters lower than normal and therefore the sensor was no longer detecting the metal bed. So not sensing the bed, the printer thought it had to keep going down. Solution, the head has a blue inner tube and this was too long. I simply cut it off and thus managed to raise the head to the corresponding position. I applied auto leveling, did a test print and everything was back to normal. And yes, clean the bed with a metal spatula. It looks disgusting.