This is a bit long, but hopefully someone will have a suggestion.
I have two FILCO Majestouch 1 keyboards, from the same batch, just under two years old (the original UK batch). One is a Cherry MX brown that's seen heavy use at work, one Cherry MX blue that's seen a lot less use at home.
The numpad - key on the brown recently started to double-type, the cause being a key that was not fully in place when soldered (the key died completed during my testing—typing with varying amounts of pressure applied to the switch—when it finally snapped into place and ceased functioning). It was a week or two at least before I ruled it out as human error and realised that the switch had a fault. At that point, the 9 key on my MX blue at home started exhibiting the same double-type symptoms. Both keys can be easily demonstrated by alternating that key with enter, leaving some lines with a duplicate character.
I also started noticing that 'r' on both keyboards would do the same, but 99.9% of the time, I cannot reproduce this with alternating 'r' and enter, making me wonder whether it's merely an artefact of my nervous system. I believe I have seen it after extensive testing, but I'm not completely convinced yet that it wasn't experimental error.
The Keyboard Company have my MX brown keyboard at the moment, and they can't find anything wrong with the 'r' key at all. In the meantime I've finally put my Topre Realforce to good use as a backup keyboard, and I don't get double 'r's on that at all. I often get double letters, but so far as I can tell that is just my typing: I have a jittery nervous system. However, I see a disproportionate amount of double 'r's, even when my finger tells me that that the key was just hit once, gently.
I would prefer to get both keyboards fixed, because it's not only cheaper, but they have sentimental value (even though the clickers are all wearing out in the MX blues) – I'd rather have my keyboards back, than replace them, even though the Maj 2 is reported to resolve this manufacturing flaw.
Is the duplicate 'r' more likely to be my twitchy nervous system? Seems weird that an undetectable fault affects two keyboards on the exact same key. Yet I can't deny the sheer number of occasions when I've got two 'r's when I feel so sure that it wasn't me. I'm worried that there are more switches on the blink that will worsen and drop off over time, with no way to detect it from examination of the keyboard. I could have the Keyboard Company them re-solder/re-seat both 'r' keys just in case, but would that be the last of it?
(I was looking down at my palmtop earlier on my lap, and heard a resounding crack and my peripheral vision darkened for 1/2 s. I suspect one of the tubes in my TFT is about to pop as well, so a new monitor may end up needing my cash! I had the Mac's CRT on behind me, and those go a real crack when the EHT arcs, but it doesn't give out enough light where I was looking to have darkened my field of view as much as a failed CCFL on my main display. Ugh.)
