Ive had the same issue on my keylab 25. Its happened on 4 different keys now. No force either. I worked out how to fix it- I had to as I was on tour using it every night. This has probably made any warranty void but I dont think Id want a replacement unless I could be assured that the design/materials issue had been resolved.
To fix it, you need a phillips screwdriver to take off the bottom panel and some super glue/crazy glue to re-attach the broken piece of plastic. Once the bottom panel is off its pretty self-explainitory if you have a mind for that sort of thing. Dont attempt if your not confidant.
Its interesting once you look inside the keyboard that you realise its pretty cheaply made, despite having the appearance of quality. They are good keyboards, but they would be the best if those keys were stronger