This is a complex situation, but you've identified some very plausible causes. Here's a breakdown of your points, potential diagnoses, and troubleshooting steps

1. The Ground Faults:
GFI Sensitivity

EV chargers use very sensitive GFIs for safety (typically around 5mA trip). This makes them more prone to nuisance tripping than a standard bathroom GFI.

Charger Issue

The fact that it faults even when not actively charging points heavily towards a problem with the Autel charger's GFI circuit. This could be a faulty component, moisture ingress, or sensitivity drift.

Wiring Issue

Although you checked, a small nick in the insulation of one of the conductors, or a stray strand of wire bridging to ground could be the culprit. Even if it initially measures fine, thermal expansion during operation could cause a fault.

Harmonics/Noise

Modern electronics (including your neighbor's welder, EV chargers, and other devices) generate harmonics and electrical noise. These can sometimes induce current in the ground wire, leading to GFI trips. This is more common in buildings with significant electronic loads.

Shared Neutral (Not Likely but Possible)

While not explicitly a shared neutral in the traditional sense, if the grounding and neutral are not rock solid, imbalances can lead to voltage differences that the GFI interprets as a fault.

2. The Flicker and Neighbor's Welder



Voltage Sag

The flickering lights and the neighbor's welder affecting your supply strongly suggest a voltage drop issue on your city's transformer. This is especially likely if your neighbor is also having EV charger issues.

Shared Transformer

You and your neighbors likely share a distribution transformer. Heavy loads on that transformer will cause voltage sag, particularly when the transformer is nearing its capacity or is aging.

Loose Neutral Connection (City Side)

A loose or corroded neutral connection at the transformer, the service drop, or even further upstream is a prime suspect. This can cause voltage imbalances and erratic behavior. A bad neutral can also cause very high voltage conditions on one leg and low voltage on the other leading to equipment damage.

Service Conductor Degradation

Old service cables can corrode, increasing resistance and causing voltage drops under load.

3. Your Hypotheses & Questions



Split Phase Imbalance

Yes, a significant imbalance on the incoming split-phase (240V) line can cause 240V GFIs to trip. The GFI relies on equal current flowing through the hot legs. If there's a major imbalance, it can appear as a ground fault.

240V GFIs and Ground

240V GFIs definitely use the Equipment Grounding Conductor (EGC) for reference. It is the only grounding element for that circuit. They don't use it like a neutral, but any voltage difference between the hot legs and ground can be interpreted as a fault.

Better Grounding (GEC Rods)

Definitely worth investigating. A robust grounding system is crucial. If you suspect the grounding is inadequate, adding (or replacing) ground rods, and ensuring proper bonding to the water pipe (if metallic and compliant with local codes) is important. The quality of the soil around the ground rods also plays a significant role. Make sure to check for corrosion at the rod clamps.

City Neutral

This is a prime suspect. A failing city neutral can wreak havoc on the voltage balance and cause GFI trips.

4. Diagnosis and Troubleshooting Steps


Verify Grounding



Inspect Ground Rods

Locate your ground rods. Are there two? Are they properly installed and connected with the correct clamps? Are the connections corroded? What's the condition of the wire connecting them to the panel?

Ground Resistance Test

Have an electrician perform a ground resistance test. This will tell you the effectiveness of your grounding system. Ideally, it should be 25 ohms or less (as per the NEC). However, even with a good resistance reading, you can still have voltage issues if the connection to the transformer is poor.

Bonding

Confirm that your water pipe (if metallic) and any other required metallic services are properly bonded to the grounding system.2.

Voltage Monitoring



Long-Term Voltage Recording

Use a voltage recorder that can log voltage over time. This will help you capture the voltage sags and imbalances that occur when the welder or other heavy loads are in use. Record voltage at the main panel. Record voltage on both legs.

Voltage Drop Measurement

Use a multimeter to measure the voltage at the Autel charger while a high current load (like a water heater or another appliance) is running. Excessive voltage drop indicates a wiring issue.3.

Load Analysis



Current Clamp Meter

Use a clamp meter to measure the current on each leg of your main panel. This will help you identify any large imbalances. Note these during peak usage and also during times when the charger faults.4.

Autel Charger Testing



Contact Autel

The fact that it faults even without charging suggests a faulty charger. Contact Autel support and see if they have any known issues or troubleshooting steps. They might suggest a replacement.

Move the Charger

If possible, move the charger to another properly wired and grounded 240V circuit (like a range or dryer outlet). This can help determine if the issue is the charger itself or something with the original circuit. Note: Ensure this other circuit is adequately sized for the charger's load, even for just testing.5.

City Utility Involvement



Document Everything

Keep detailed records of the voltage readings, fault occurrences, and any other relevant information.

Report to Utility

Contact your power company and report the flickering lights, voltage fluctuations, and the fact that your neighbor is also experiencing issues. Emphasize that multiple residences are affected and that it's impacting safety-critical equipment (EV chargers). Present your documented evidence.

Request Neutral Inspection

Specifically request that they inspect the neutral connection at the transformer and the service drop to your house. Explain your concerns about a failing neutral.

Neighbor Coordination

Talk to your neighbors and encourage them to report the problems as well. The more reports the utility receives, the more likely they are to investigate.

Escalate If Necessary

If the utility is unresponsive, escalate the issue to their supervisor or regulatory agency.

Important Considerations



Safety First

Electricity is dangerous. If you're not comfortable with any of these tests, hire a qualified electrician.

Code Compliance

Ensure all work complies with the National Electrical Code (NEC) and local codes.

Documentation

Keep records of all tests, repairs, and communications with the utility company.

Specific to Your Situation: The firestorm and damaged infrastructure add another layer of complexity. There's a higher likelihood that the utility's infrastructure was affected.* The neighbor's comment about their Tesla chargers "erroring randomly" is a significant red flag. It strongly suggests a problem on the utility side.Good luck! This is a challenging problem, but by systematically investigating and documenting your findings, you should be able to isolate the cause and get it resolved. Flag for review