I need help in fixing the sound of F1 diesel motor sound is always on with different addresses set on the decoder and with different controller address.

The loco is from about 2005. It is the Marklin NY Central ALCO. It uses a decoder with 8 dip switches (this one actually has 10, but the 9 and 10 are not used.)
1) When the address of the lok is set to #49 using the dip switches, and setting the controller to 49, the F1 diesel motor sound is on, the F2 bell sound can be used on the buttons and makes sounds, and the F3 horn works. I use the 6021. The loco runs.
2) With dip switch at 49, when I set the controller to 48, the F1 diesel motor sound still is on, but the F2 and F3 buttons do not work for the bell and horn. The loco does not run.
3) When I change the address on the decoder using the dip switches to #48, and set the controller to 49, the F1 still makes the diesel motor sound, and the F2 bell and F3 horn do not work. The loco does not run.
4) When I set the address on the decoder to #49, and the controller to 48, the F1 still makes the diesel motor sound, pressing the F1 button doesn't do anything and does not shut the sound off. The F2 and F3 buttons do not work.

In summary, my F1 diesel motor sound is always on all the time no matter what address is chosen on the decoder or what is set on the controller. To run it now, I have to dial the sound to zero on the decoder.

Anyone has had this sound problem before?, and were you able to correct this. Wondering if there are any wires I should check. Thanks, Bill L.

Thanks KiwiAlan.
I press the F1 button on or off, it does not make a difference, the light on F1 is on or off, and the diesel motor sound continues to make the noise.
My other Union Pacific ALCO PA loco behaves normally.