Frame Challenge: Switch to Hardwired Connection

(But with an oops, see below. But despite the oops, I am posting this answer as OP may actually agree and in any case future people reading the question may be helped by this answer.)

People use a plug/cord/receptacle because they're used to it.

But think about it: Once it is working properly, how often will you unplug the Tesla EVSE (a.k.a., charger)? You probably won't even take it on vacation - you either use the emergency plug-in 15A 120V cord (slow charging, but works if you have nothing else; which you should keep in your car as an emergency backup) or you stop at a Supercharger. Do you have anything else (e.g., welder) that you plug into the 14-50 receptacle occasionally? The vast, vast majority of people do not.

Now look at it a different way: Do you unplug your furnace/air conditioner (excluding window units, of course)? No. You can't - it is hardwired. If you have an electric water heater (tanked or tankless), do you unplug it? No. You can't - it is hardwired. (I would use the same argument for oven, disposal and dishwasher but some people actually have those plugged in to receptacles (mine are all hardwired) - but even then they never unplug them except for repairs.)

Unless you need to move the EVSE frequently or use the 14-50 receptacle for something else, there is no good reason not to hardwire the EVSE instead. There are, generally, three things to consider:

• Disconnect. As I understand it (the code experts can correct me if I'm wrong), you need a disconnect of some sort visible and within a certain distance of the EVSE so you can shut it off in an emergency. If it is connected to a breaker in a panel in the garage then you're all set. If not, you may need to add an actual disconnect, which actually is not a big deal. Here is a GE 60A disconnect from Home Depot:

and the great part - it costs all of about $15!

• Wire Connections

When you connect together wires for a typical 15A, 20A or even 30A circuit, most people (in the US) use wire nuts. Cheap and easy. They are not necessarily available in the sizes you need for use with 50A circuits. But guess what? The disconnect will connect to big wires, so you've killed two birds with one stone.

• Device Must Be Designed for Hardwired Connection

This is the oops. I assumed, incorrectly, that you were trying to use a Tesla wall connector. You are actually using (stated in the question) a mobile connector. The mobile connector is designed for plug/receptacle use. The wall connector is designed for hardwired use. In fact, the wall connector says Do NOT install cord-and-plug type connections. (It also says disconnect not recommended, but allows it and in fact it may be required by local code, but if you don't need a disconnect then you can connect the existing wires directly to the Tesla Wall Connector.)

Unfortunately, the Tesla Wall Connector currently costs $400. Which is actually a competitive price compared to 3rd-party EVSE equipment, but only you can decide whether it is worth getting this. It is arguably the right way to install for your primary (e.g., home) charging location.