What's wrong with my wireless keyboard if some keys doesn't work properly (can't press down) but getting better some hours later?
Software cannot adjust nor control how these keys respond so it's definitely a physical issue. Additionally, software isn't going to pick the evening to make one or two keys harder to press and then relent in the morning.
If it's feeling weird and responding slowly is because something is breaking down or you have a containment build up. It could be the mechanism or one of the layers - insulating or conductive - that has an issue.  The fact that you're having an issue in the lower left hand corner where ⇧ Shift and ^ Control and  have their contact points (there are two for Space) leads me to believe there is some sort of containment/corrosion on the conductive PCB layer.  Until you open it, you won't know for sure.
Keyboard key stuck or not being recognized; how to fix
Unfortunately, these keyboards are designed to be disposable so there really is no fixing it. The keyboard assemblies are now held in place with plastic &quot;welds&quot; (the plastic posts are melted down like rivets) to hold the assembly together.  You'd have to cut all of these welds off and then find a way to re-glue everything back together.
Something that's just over a year old and barely out of warranty is worth a shot with Apple support.  These are expensive accessories and should have issues so soon.  I would give it try to see if they will replace it for you - the worst that will happen is that they decline the replacement and you have to buy a new keyboard.