Either bad switch...
Or if the MC has a residual pressure valve built in (common), or if one was added, there could be a few PSI held in the system and holding the switch on. Perhaps that model switch is an extra low pressure to operate and one a few PSI higher will resolve the issue.
Another possibility is the pedal is not adjusted properly and needs more free travel at the top, let the MC fully return and relieve pressure.
One test for bad switch or these other possibilities is with the light on dim as is the problem crack one brake bleeder screw to relieve pressure if any. If light goes off then switch is probably not bad but may yet be to low of a pressure to operate correctly in the system.
