The signal LEDs on a module in a Sensor rack should dim in proportion with the load(s) that module talks to.
If the loads dim normally but the signal lights stay solid green or dark, there could be an issue with the module or signal distribution card.
To determine if it is a module or card issue, the best troubleshooting step to take is to swap a suspect module with a known good module. If the issue follows the module, it is a module issue. If the issue stays in the slot and the module signal light dims in another slot, it is a signal distro issue.
You must fully power down any Sensor racks in order to swap components around. Swapping components around while the rack has live incoming power can results in serious injury to yourself and/or damage to the equipment.