Disconnected wire unit between the Signal Backplane and the LPS module.

Reconnect the wire unit between the Signal Backplane and the LPS module.

Disconnected wire unit between the “CTRL IN” and “CTRL OUT” sockets of the LPS units.

Reconnect the wire unit between the “CTRL IN” and “CTRL OUT” sockets of the LPS units.

Malfunction of one of the LPS units. The orange LED (Heartbeat) of the malfunction LPS is not blinking.

Replace the whole LPS module. See "Removal of an LPS module".

Defect Signal Backplane.

Replace the Signal Backplane.