Here you see a Yamaha FS keybed taken out of a Korg M1 synthesizer.

With the keybed removed, you can add and remove key caps.

But fixing some contact problems might be easier if you detach the whole contacts assembly.

For full access to the contacts, remove the screws holding the contact assembly to the keybed.

Two of the screws are marked with red tape in this photo.

If it's a Korg synth, the screws are probably black.  If it's a Yamaha synth, they're probably gold.

This photo shows the contact assembly after removal from the keybed.

These contacts are all good.