This phenomenon likely stems from the foam packaging pressing onto the key for a longer period of time so that the silicon cylinder sitting below the key lost its elasticity. See "maintain the keyboards longevity" in the entry section of Osmose's manual.
The foam packaging has been adapted in the meantime. If your Osmose shows this issue, please contact our Osmose tech support team and provide a photo of the phenomenon. We will happily provide a replacement cylinder for free. Replacing it is easy and only takes 5 minutes.