Raspberry Pi 4 won't boot with current sensor connected
Having a voltage on ANY pin of a chip while it is not powered is generally outside the normal operating conditions, so normal operation is simply not guaranteed and funny things can hapopen.
I suspect that the ADC passes the voltage on A1 via the 3.3V or one of the SDA/SCL lines back to the Pi, which causes it to be outside its normal operating conditions and hence malfunction.
Check: your LEM sensor has a VERY low output impedance: 5 Ohm, hence it can deliver quite a current, which could cause the problem.
Fortunatley, your ADC has a very high input resistance (M-Ohms). I would start with a series resistor of 10k in the A1 line. That limits the current into the A1 input, but doesn't significantly affect the measurement.
If that doesn't help, add a bleeder diode (try 1N4148 for a staret) from the ADC A1 input to the 3.3V, and a 1k bleeder resistor between the 3.3V and ground.