Paradise19, are you in the USA?

Set the split point to the far left hand "C" and see if all the keys are in tune now. (you will not have APC unless you are in the pianist mode for this test)

My guess is that the pitch bend wheel pot or circuitry is bad which may or may not have been caused by a shock such as dropping. There would be obvious damage to the case if it had been hit that hard.

There is excellent service available in Florida . . .