Engine Failure Hazard

[MajorStare]

I have a MY2020 that I purchased in October. It has had some use over winter, possibly a run out once a month.
When not used it is garaged and fitted to an Optimate 2 Battery Charger & Conditioner.
Both lights on the charger will go green after a few hours of being plugged into the car battery.

Today I have driven 15 miles, parked up for an hour, then returned home 15 miles.
5 minutes later a 5 mile drive to the petrol station to fill up (range was 40 miles).
2 miles after leaving the petrol station, pulling away from traffic lights, the car changed to second and as it tried third it seemed to jerk, it couldn't change gear and showed Engine Failure Hazard, Hill Decent Inactive, start/stop Inactive, with yellow spanner light.
Car went into limp mode.
Turned off and on but no better.
Turned off, waited a few minutes and it ran fine, getting me home (a steady drive).





I'm thinking (hoping) it's battery related
This is the battery. No dates on the battery.



I'm hoping it is the battery.
After a long run and connecting the car to my conditioner/charger, it shows a yellow light to say the battery needs charging and it takes a few hours to turn green. This makes me think (hope) it is the battery. Although it always starts without issue.
But, why today, not other days when it's been used?

[NewtonSheep]

I had a similar experience a couple of years ago, although mine said " gearbox failure". Nearly gave me heart failure!

Left it a couple of hours, re-started with no problems. Limped home and took to dealer the next day. They put it through diagnostics and 'found nothing', but 'did a software update anyway'. Been faultless ever since.