The problem lies with the membrane inside. A keyboard has two membranes separated by a thin piece of silicon or plastic the same size of the other membranes. Where the key's are located, there is a hole so when you press a key, it pushes the top membrane onto the bottom and makes contact, sending a signal though for processing.
When liquid is spilt onto a keyboard and goes inside, it goes between the membranes and makes contact on the various contact points. Liquid conducts electricity and therefore the keyboard thinks a keystoke is being made. I've washed keyboards in the past but unless they're super expensive, it's not worth the hassle.
In order to properly clean it, you'd need to unplug the keyboard and leave it for a short while, to allow for the electric charge to fully dissipate. Then, open the keyboard and remove everything, be very careful with the connectors and the membranes as they can easily be damaged.
Wipe everything with a microfiber cloth, allow to dry naturally, then reassemble. Be careful of static as it'll render the keyboard inoperable and can happen in a flash.
It's normally better to just replace the keyboard.
Please don't bother with any software settings, scans, changes or anything else. The problem is your keyboard and the short circuiting of the membranes inside. Even when it dries, it may still allow the contact to happen and cause a problem.
Hope this helps.
15 years in the IT Industry