What we refer to as "the fusebyte failure" was a manufacturing programming issue on Revision D and earlier controllers. This manufacturing defect led to the controller firmware becoming corrupted after some period of normal operation (days, weeks, even months). Symptoms involved sporadic controller functionality typically leading to complete controller failure (controller unable to turn on). The issue was resolved in all bikes produced from mid-2016 onwards and is completely eliminated in any bikes from that date forward. Bikes built before that date (which did not have their controller replaced) still risk this latent failure occurring. This is characteristic of five speed Porteur S's and Porteurs with Promax brakes. Should this issue occur, the controller will need to be replaced with an updated version.