The board that you would replace is here -
However, if you investigate you should be able to reposition a spring and/or replace it so that the buttom works.
This type of button or spring (if you find you can remove it) would be available as a more generic electonic part.
If you contact LG directly they should also be able to advise you. You may still be covered under the MfG warranty. They tend to cover their electronics (parts) longer than some other Mfgs. This info is in your owner manual.
Please let me know if I can assist you with anything else or you have another question about it.
I haven't dissassembled this unit. Most units of this type require you remove an access panel at the bottom and then work your way up. If something doesn't come off easy then there is probably a screw or better way to approach it.
However, another expert has advised me that LG will actually give you instructions over the phone to help the consumer do their own repair.