I'm really sorry to hear about the problems you are having.
What type of relay board are you using, low-level trigger with opto isolaters? And the connection from the Pi > shift registers > relay board is just control wires and +5V to vcc on the relay board with the ground not connected?
The 24V through the relays should be completely isolated from the 5V circuitry.
Also, if the relays are acrive low, there needs to be a voltage to the relays to pull them high to keep them off. If there is not enough power to the pi/shift registers that could cause the relays to switch on. I prefer to use active high (high level trigger) relays which only switch on when a voltage is applied.
What type of relay board are you using, low-level trigger with opto isolaters? And the connection from the Pi > shift registers > relay board is just control wires and +5V to vcc on the relay board with the ground not connected?
The 24V through the relays should be completely isolated from the 5V circuitry.
Also, if the relays are acrive low, there needs to be a voltage to the relays to pull them high to keep them off. If there is not enough power to the pi/shift registers that could cause the relays to switch on. I prefer to use active high (high level trigger) relays which only switch on when a voltage is applied.