My 2014 Macbook (the one with the 'retina display', gold finish etc.) typing lacunae

A lot of the letters I try to type are not appearing unless I type very slowly.
Possible reasons:
Heatwave, affecting my delicate-but-oh-so-elegant 2014 Macbook;
MacOS Sierra issues;
My own forgotten-and-likely-strange settings;
New experience, as of today, Sunday, 30 July, 2017.

The same sometimes happen to me but I have tracked down the error to most likely be dust/litter underneath the keys. Blowing hard and “force-pressing” the malfunctioning key several times (like tap dance) has usually resolved the problem. It usually affects keys that are less commonly used on my gold Macbook.

I get this problem on my MacBook Pro (the newer one with the same keyboard). It’s probably debris or small amounts of moisture, as I’ve noticed the problem is usually more defined after it’s been sitting around all night, and after a few hours of “warm up” the problematic keys go back to being fine—the “tap dance” sometimes works for this reason.

Unfortunately for me, one of the keys that gets stuck a lot is the spacebar!

My early '14 macbook air has never had this issue. And I am not neat.

I forget the models, but Apple has gone to the butterfly-type keys. I wonder if the new design is a problem. I think I shall sit back, keep typing on my beater, and see what shakes out from the keys of other’s machines.

My 2013 MBP has the old keyboard and does not have the problem. My 2015 MB with butterfly mechanism has it, but not my 2017 Apple bluetooth keyboard.

The MacBook Air has the better older keyboard—the one Apple used for many years. The new ones with this issue are very thin, have hardly any gap around the keys and have very little travel—they are also a lot louder than the older keyboards. In general they seem more fragile—in fact I had to have the keyboard on my 12" replaced after a year because I had actually worn through the plastic on three common keys and the spacebar; the backlight was shining through them. That keyboard had sticking issues as well which is what prompted me to bring it in before the AppleCare expired—they seem to have a design flaw or two.