GPIO Poweroff 'blink'

Hi

I've configured the GPIO Poweroff in pCP 'Tweaks' tab to GPIO17 'Active Low'.
When pCP is running, the connected relay to this GPIO is energized, and all is working well.
When I reboot pCP the relay gets energized upon boot.

BUT:
When I issue the 'Shutdown command', pCP shuts down and before the relay is completely powered off, it 'blinks' once.
So the state goes from ON to briefly OFF, back to briefly ON and then remains OFF.
What might be causing this behavior?