I noticed on the relay board that R6 and C3 are not populated. This snubber protects the chip from the inductive kick of the relay coil. The values are .1uf and 100 ohm. The alternative is a clamp diode (1N4004) across the coil on the back side of the board with the cathode on pin 8. The snubber or diode is necessary for proper operation.
These days I use the diode and install an LED and current limiting resistor in place of the snubber. The LED lights when the relay pulls in. The clad will eventually get changed when I run out of the existing stock.
I did the same, and put the green Led on the front panel, as the "on indicator" on all my phase amps. Nice to know the delay is working properly, and the amp is healthy.