Charging slowly, fault light on mobile charger

My 2018 40kwh Leaf is charging about half it's normal speed with the level 2 mobile cable that came with the car.

I'm using a 240V wall socket that I've been using for years. I have another EV that I charge from the same socket (with no problems).

When I plug the mobile cable into the wall, the red fault light comes on. Once it starts charging, the red fault light stays on. The green and amber lights are flashing.

I took it to the dealer and they claim they couldn't reproduce the issue.

It charges fine on a public level 2 charger.

I'm about to buy another mobile cable on Amazon to see if that's the issue.

Any ideas before I do that?

What's the make a model of your portable charging unit (EVSE)?
Is it the Nissan OEM (by Panasonic) portable EVSE that came with a new 2018 Leaf (see link to pic below)?
https://teslamotorsclub.com/tmc/attachments/2018-leaf-evse-jpg.273380/?id=2512109

If it's the Nissan portable EVSE, then check the voltage on that 240V wall outlet. This type of EVSE needs at least 220V to properly work. There are posts on this forum where people have about 208V at their outlets and had issues with the Nissan portable EVSE not working because of that low voltage.

Has that portable EVSE ever worked well on your 240V wall outlet?

Yes, it's the same EVSE as in your picture. Model #296900

The voltage coming out of the outlet is fine. In fact, I can monitor it while charging a different vehicle. That vehicle usually charges at 239V 32 Amps.

I've been using this EVSE that came with the car for almost 5 years without any issues until now.

I went ahead and ordered another mobile cable on Amazon. If it doesn't work, I will just send it back.

The Nissan EVSE should be covered by the 5-year, 60,000-mile EV system warranty if you can convince the dealership that it is defective. I think it has a temperature sensor in the plug and reduces charging current if it thinks the plug is getting warm. I rarely use mine at 240V but use it with the 120V adapter to run my portable generator under load periodically. I have noticed it drop to 6 amperes (instead of 12) once in a while and suspect its temperature sensor is limiting the current.

Update:

Well, my new cable (EVSE) already arrived from Amazon. Good news: it fixed the problem.

Bad news: now I have to try to convince the Dealer that the original cable (EVSE) is bad. I'm at 58k miles, so it should be covered under warranty.