An image forming system includes a substrate transport unit, an image forming module, an event sensing module, a heartbeat generation module, a signal detection module, and a repositioning module. The substrate transport unit may transport substrate including at least one splice along a transport path. The image forming module may form an image on the substrate. The event sensing module may detect an event and provide an event signal along a signal path in response to the event. The heartbeat generation module may provide a heartbeat signal different than the event signal along the signal path. The signal detection module may determine a presence of the event signal and an absence of the heartbeat signal. The repositioning module may move the image forming module from a first position to a second position in response to a determination of the presence of the event signal.