This is a hard one to nail down. There are two possibilities, the panel itself has failed with micro fracturing due to something heavy banging on it or even heavy pressure from your fingers where the upper uppercase is a bit thin so it’s flexing under the pressure so over a period of time the panel fatigues. The other is the cable unit either became damaged or a solder joint if failing either at the connector or the components which are on it. I would first try the cheaper and easier which is the cable [product|IF123-074] then replace the panel.