Moen Vertical Spa

The shower jets (not the shower head) all have water running when the valve to turn them on is not engaged with the shower running. Is this a valve issue, or O-ring, or washer, cartridge??? I have managed to get the valve/faucet assembly taken down to a point, but after that, I see no way to remove the valve to check for wear/tear, etc. I don't have the model number or name of the assembly... it was here when we moved recently moved in.

Thanks for your help.