One good way to tell if the connection is good or not is to measure the temperature of the connector using a noncontact infrared temperature sensor. You can buy them at Lowe's, Harbor Freight, or similar stores, and they're about $20. Also good for measuring the temperature of your tires. They do not tend to be super accurate, but are still very helpful, especially if you're comparing, say, one part of the plug to another part of the cable. Any poor connection will manifest itself as heat. Some heating during heavy charging is normal, so if you get this tool, take a couple measurements during normal charging, especially at high Amp loas. It's the current, not the voltage, that leads to heat.
Of course, it's possible that a connection is fine one day and not fine another day, due to dirt in the plug or whatever. There are electrical plugs that can lead to fires on EVs, so this is not a bad idea at all to have in your toolbox even on a professional installation. It will heat a lot more when the KWs are higher than when lower.
Because all EVs are hard on tires, it's good to keep the Thermal Sensor 'gun' in the frunk and check the tires on longer trips.