Oh great... WORSE thing you can do is to spray in Deoxit or Blue shower contact cleaner inot pots or faders!!!! It destroys the lube on the resistance element !!! The ONLY place to use those products is on metal switch contacts.
You have ONE chance to try and restore it without replacing it...
Go to Home Depot and in the electrical dept find a can of CRC226 (about $2.70 Bluish can) Use ONLY this product CRC226 as there are other CRC products there that are NOT applicable to this problem...
Now with the spout flush this down where the other cleaner had been put and work the control... Worse case is if you can't get enough into it you might have to open the case to get at a place you can spray into the pot where the lead wires go into it...
I use CRC226 to restore volume and gain pots in many guitar amps that become noisy. Usually I do it from inside the amps where I can get to the slot where the leads go into the pot. The product is for electrical stuff and is a water displacer but not gunky like WD40... never use that product in controls or switches... it is essentially fish oil. CRC226 is also goo to protect tools from rust.
I hope you can fix your unit without replacing the pot...
First though, flood a bunch in and then TURN the keyboard upside down so the CRC226 floods over the resistance element inside the control and work the control.
In case you need to replace the pot here is the info and part number from Roland.:
5 02455234 POTENTIOMETER 12M/M ROTARY POT. EVJY15F02B14
Here is an Avnet catalog page but they only do large orders of 1200 which is 1199 more than you need.
The pot is a Res POT 10K Ohm 20% 1/20W 6mm Pin Snap-In It will be a "B" taper audio type.
Here is link to your service manual for the Juno D: