One key is not returning to it's raised position; no key action.

is it under warranty ?
if not
you may have to contact your point of sale to find their local repairer

if you cant un stick them yourself that keyboard will have to be taken apart

are the two keys ... white keys or black ...nearby or way apart
do the two keys drop loose..and lift up
or stay down
example will vacuum cleaner suction help lift the stuck keys or not

sales blurp says this
A spring-less hammer system
Scaled Hammer Action Keyboard

https://www.jbhifi.com.au/musical-instruments/casio/casio-cdp-120-digital-piano/91120

There is a well documented problem that occurs with the keybed on some of these models due to a manufacturing fault. Take a look at the keys that are sticking. Is the gap on either side of the key the same ? If not then the key normally leans slightly to the left rubbing on the adjacent key causing the sluggish action. The fixing tab at the back of the key breaks causing the spring pressure to push sideways.

You can just replace the offending key but the problem will eventually return. You could replace the whole keybed but this is a very expensive fix.

Keys are around £ 15.00 each.
Replacement keybeds around £ 450.00

Visit www.beckettsmusic.co.uk

Search for VU101 via the search box.

There's probably a broken return weight or two. It's easy to remove the keys and get to the weights below them AFTER the keyboard bed is raised slightly.My email address is [email protected] if you have any further questions.

Call Yamaha at 714-522-9000 and ask for a tech who works in your area. Attempting self repair could void any garuntee that is covering the problem.

Might want to rethink that....to raise the action is to have the strings higher off the fretboard....if you shim the neck in relation to the body, you'll actually lower the action. To raise the action you need to raise the height of your bridge/saddles. If you want to lower the action and the bridge/saddles are as low as they can go you could remove the neck and insert some card - might have to do some trial and error but to my mind...to shim enough to significantly lower the action, would take a thick shim and you might not get a good tight fit between neck and body. You might actually need a truss rod adjustment - not an amateur adjustment.

The unit will have to be opened and the key restored to the normal position. Most have a spring, sometimes a leaf type that holds the key up and locked in. When opening the unit care must be used as there are ribbon cables between the halves of the cover.

The bridge should be on two posts, both of them with knurling on the edge. These screw into the body of the guitar, allowing you to raise or lower the action of the strings. Turn them clockwise to lower the action, making sure to turn them the same amount, so as to keep the strings even. You WILL have to re-adjust intonation after this.

Hope that helps!

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/cameron_463100ffd54b591d

Hi there,
you'll need to open the keboard and check for the keys that has a missing mechanism on it. It usually is a stopper to prevent the keys from "sticking". You can use crazy glue or mighty bond to stick the broken parts together.

Hope this helps

To fix the action on your B.C.Rich Warlock, you need an Allen Wrench, or Hex key. There is a truss rod cover on your B.C.Rich's headstock. Just open it using a screwdriver and you will find the truss rod. Then adjust the action using the hex key.
check out more here -
http://www.squidoo.com/b-c-rich-warlock-set-up-and-fixing

There is OFTEN a felt strip that the keys come up against at the lip of the case, either near the end of the keys or right where they disappear near their middle. SOMETIMES this strip gets knocked off.