Fix MacBook: Repair stuck spacebar butterfly keyboard
Many MacBooks are still in use with the Butterfly keyboard, no matter if it is the 12" Retina model, the MacBook Pros or many MacBook Air. Apple replaces defective keyboards up to four years after purchase (so check out the repair program here), but some models may be older and the error will still occur, of course.
MacBook space bar sticks
The biggest problem is the space bar: in the worst case, it hangs or simply sticks or doesn't come up anymore. Of course, the entire keyboard is no longer usable. You can either change the whole keyboard (yes, that's possible with the 12" model, everything is screwed together like on old MacBooks and replacements are available here), but since you don't have anything to lose, you can first try to get the space bar back in place.
First, you have to carefully remove the space bar (in this example, it's a MacBook 12 2015). To do this, go between the key and the aluminum case with a thin object and unlock the four small plastic hooks of the space bar, which hold on to the upper metal strut. A thin cutter knife works well if you are careful not to scratch anything. On the photo you can see where the fasteners are. Do this carefully and with patience. Then the upper side of the space bar should be exposed. Then lift it carefully and pull it away upwards. This should be quite easy. The lower four points are not clipped but only hooked, so don't break off, the key can be removed quite easily.
You may find dust and other dirt here, but even after cleaning it often doesn't get any better. If you look at the construction, you will immediately understand why: Apple has given the entire space bar a metal spring, as much as any other key. The problem is that the space bar has as much mass as five normal keys plus the metal struts in the construction, which also have to be lifted. It should be clear that this spring is no longer strong enough at some point.
Relieve keyboard spring through less friction
Now the small spring has to push the entire space bar upwards against the earth's gravity and is actually not strong enough for this. Since we can't do anything about the mass of the key or the acceleration due to gravity, we have to turn the third wheel: the friction of the butterfly mechanism. The white plastic parts are clipped into the transparent holders on the board with simple plastic lugs. Probably they are connected beforehand and then glued together. However, we need to carefully pry out the construction. Try one section at a time. You'll see that in each case the top half has four retaining tabs across the entire width, and also four on the bottom. Even if these look totally clean, friction seems to increase here as well over time.
Warning: we've also had the case that a working space bar didn't work anymore after removing and reinserting the butterfly mechanism. So the slightest change immediately leads to failure. So if your space bar is working, leave it as it is and blow on it for now.
But we have the case that it already sticks. So we try to make life easier for the little metal spring and reduce the friction of the mechanism. And for this we take the knife: just cut cleanly every second pin. One on the bottom, one on top, one on the bottom, one on top. So now every second pin is missing, yet the spacebar is still neatly guided. Maybe you can also do top, bottom, bottom, top (the main thing is symmetrical), but you have to test that yourself. In any case, the alternating variant worked well for us.
With half of the fastening points missing, half of the friction in the mechanism is also missing. And believe it or not: the space bar works like on the first day! The whole trick is just to relieve the undersized spring. This makes the entire keyboard usable again!
To reassemble everything, put the remaining lugs back into the transparent holders (The symmetrical cutouts with the metal bar facing up). You can simply hook the first one cleanly, the second one with a little bit of feeling as well, and the remaining ones with a little bit of pressure. Then hook the space bar with the lower four points back into the butterfly mechanism and then clip it into the four retaining points at the top.
A complete replacement of the keyboard can thus be avoided in most cases. But once again, if the butterfly mechanism is removed, then the removal of half of the retaining lugs is almost mandatory.