Yamaha CLP 930 Key issue

I have been working on repairs for my school and my family. One of the keyboards I am working on is a CVP 930. Before, it had only lost sensitivity in one key and the other keys were sluggish, so I cleaned the contact board/strip and scrubbed the keys. However, when we put it back together and tested it, something really odd happened. Whenever you press a C and a G in any octave, a loud B-flat above said G will play along with the C and G. Similar issues also happen with any note above an E-flat play in combination with a G. As said before, this happens in all octaves. When I play the keyboard using one key at a time, It sounds fine. I have tried testing the connections and diodes, but everything checks out. Is this a problem with the YMZ702-D key scanner, the contact board itself, or the motherboard?

I apologize, every time it said “CVP-930” I meant to say CLP-930. That’s my mistake.

I am betting that the key contact strip is not aligned or installed correctly. It’s one strip across the entire keybed, and there are breaks every so often in the conductive black lines on the rubber strip. If these aren’t aligned with the keys correctly, then you will get strange key behavior. I believe in that model that there are alignment holes in that strip, so make sure those holes are in the right places. Another possibility (if the holes seem aligned) is that the strip may be in backwards - flip it around, and that may solve your troubles.

Ah, thank you so much for your input. I’ll do this ASAP. this will help a lot. I can’t convey how much I am grateful for you.

Btw, rock on, you’re the best for keeping synths alive