Try removing the keys and cleaning the contacts etc. with Isopropyl Alcohol 90%+ and then allowing them to dry completely before replacing them. Also don't get them mixed up after you take them off.
Here is a link to the Ifixit guide to repair your laptop.
A bit over the top perhaps but I suggest that you remove the battery before you start removing the keys, to prevent the possibility of more problems occurring through a mishap during the repair process.
Samsung ATIV Book 9 Plus Repair
If you need replacement keys here is a link to a supplier. Just search online for others if this doesn't suit you.
Hi @tjwreckless ,
My mistake apologies. It may be that you have to remove the key and clean the hinges etc as they may be 'sticking' due to the dried liquid residue.
Here is a link to a video that shows you the priciple of key replacement etc. I would still recommend using Isopropyl Alcohol 90%+ as it leaves no residue.