Roland f-50 First 7 right hand whites keys appear to have lost volume and sound off / flat.

One of the lines in the keyboard scanner has opened up. I have an idea what it might be and it is a nasty problem involving circuit traces that are silver conductive paint on a plastic insulating base that separate from a jumper at each end of the strip that the key contacts are made by conductive rubber pills pressed down by the keys. The contact of the flexible circuit under the keys to the jumper cable can be broken by vibration. I have an EPS7 with the problem and other than replacing the whole contact strip under the keys it really has no easy solution.You should probably have a Roland shop look at this problem. If your unit has this same arrangement it is repairable only by replacing the whole key contact strip.