Yamaha p125 touch sensitivity problem

I have Yamaha p125 and the D below middle c suddenly only produces sound at maximum volume. Any suggestions? Could this be humidity related, as rain has been torrential lately and humidity is in the 90% range

Assuming there has been no events lately, like a soda spill (most common keybed killer) . Probably a contact strip that needs cleaning or replacing. Likely an inexpensive easy repair.

No events. Thanks for the info. Now I’ll get to learn how to use it.

The contact strip prob has dust or dirt interfering with the function of the D key. You will need to take they board completly apart (every screw on the bottom), then take the cable support (3 screws) off, detach the ribbon cable from the main board (carefully pulling it). Then there are 8 screws visible under the hammers that need to be taken ont.
this will relase the keyboard from the botttom of the case. Once this is accomplished, the keys need to be taken off (unscrewed) where the D key is and one group of keys below and above the bad key.(These keys are groups of octaves.) At this point you will need to pull off the rubber contact strip, inspect and clean it with compressed air. DO NOT use any liquid or spray cleaner which will only make the problem worse…I guess you’ve figured out that this is not a simple fix…and maybe you should call
Yamaha Service to find a qualified technician in your area…just sayin…

Thanks for the response and the blow by blow how to info. I suspect your diagnosis is dead on and am now debating whether to attempt repair or take the 200 mile five hour round trip twice to drop it off at the nearest yamaha service and then pick it up again.

Is the keyboard still under the 3 year warranty?

Yes. It is the 400 miles/20 hours of travel to get it to a Yamaha service center and back that is the problem.

Did you get my message ?