I had the same problem,so I decided to turn the whole thing apart . Different model but same arrangement of keys. I dismantled all ALL the keys and unbolted all the screws, until I got down to the main board of the piano. I identified the problematic key (D, 15th or so from left to right). When the key was played, all the others around it would have a random loud tone. I found the sensor for that problematic key and guess what? Over it was some kind of dirt, like a dry stain of liquid, probably from a spill. I link a picture of something similar. I proceeded to clean it, tested and worked perfectly!
I actually enjoyed the process of dismantling the piano and understanding the issue, fixing it and put it back together.
In short, the solution is simple, but it takes time, patience and care t get to where you can apply it
I hope this post helps
https://photos.app.goo.gl/2wnkaZkfnAW9e9426
https://photos.app.goo.gl/hsJj6BzFKXx6rHH59
