I gave up on three Kinesis Advantage keyboards in 2006, after they all started dropping key-up events on modifier keys. I then took one apart. Primitive, dated USB hardware, and nothing about the company read that they were eager to modernize. (The ergo keyboard market abounds with never-updated designs.)
Has there been a generational improvement in their circuit quality?
The original ones had some problems that were never fixed (IIRC, the original firmware was outsourced to a company that went under), but the Advantage 2 was a redesign and works great (at least for me).
I had the same bug and it irritated me to no end too. I was about to make my own custom controller when I found out that they made a version 2 which fixed the issues. I have 2 of the version 2 and have been using it for a few years now with no problems. I'd say it was improved.
If you email them, they might give you a discount or some kind of trade-in if you tell them about your previous problems. I've found their customer service to generally be pretty chill.
Is that what's happening? My kinesis advantage (plugged into a Mac) sometimes gets stuck modifier keys and only unplugging it and plugging it back in fixes it. Seems worse than just dropping some keyup events, because it doesn't get unstuck if I hit the modifier key again.
Not Advantage, but my Kinesys Freestyle Edge has great firmware and customize app (Swing) that works flawlessly. The firmware is better in some features than QMK, but worse in some features. (I want LT key on QMK for Kinesis)
Has there been a generational improvement in their circuit quality?