When your MX Keys types "aa" instead of "a", it's a debouncing failure: the keyboard detects two presses for one. This issue mainly hits heavily used keys (space, enter, common letters) after 3-5 years. Three causes: tired mechanical scissor, buggy firmware, or matrix defect on the PCB.
Diagnosis
Quick test to isolate the cause: if it happens only on 1-2 specific keys = tired scissor (€6.99 replacement hinge). If it happens on random multiple keys = firmware or matrix. Disable all autocomplete software and test in a raw text editor to rule out software conflicts.
How to fix it
- 1
Update MX Keys firmware via Logi Options+ → Settings → Update.
- 2
Disable autocomplete tools (Grammarly, etc.) that can introduce double characters.
- 3
If a specific key doubles, remove it and inspect the scissor — tired = €6.99 replacement hinge.
- 4
If it persists on multiple keys after firmware + cleaning, matrix issue — motherboard at €14.99.
FAQ
What is keyboard debouncing?
Algorithm that filters electrical bounces when a key is pressed. The metal contact bounces for ~5ms, the firmware reads those bounces as a single press. If debounce timing is too short or the scissor is tired, bounces pass through.
Does double-typing worsen over time?
Yes generally. The mechanical scissor wears out progressively, contacts become less sharp, electrical bounces last longer. Firmware cannot compensate indefinitely.
Can a firmware update worsen double-typing?
Rarely but possible: Logitech has previously released firmware that altered debounce timing. If the update didn't fix or made it worse, you can downgrade via Logi Options+ (Settings → Firmware history).
On an MX Keys, double typing most often comes from the firmware or a tired hinge. Five minutes of diagnosis, and a €6.99 replacement hinge if needed.