Lifetime fill of transmission fluid is the most absolute bullshit ever concocted, wonder when they will do so for engine oil in the future...

Failure of transmission after fluid change usually when :
1) over/under fill
2) use wrong fluid type
3) if use those rtv gasket paste, applied too much till some fall off and get stuck inside the fluid circuitry. Those with normal physical rubber gasket unlikely will have this type of problem
4) if already very high mileage, don't change. The gunk accumulated inside is ironically what is making the actuators and friction plates work. New fluid will just wash away those and cause slipping.
5) if change transmission fluid using dialysis machine, another possible cause is wrong timing/temperature/pressure setting.
6) someone act smart and use the "flushing" method which is very risky for newer type of transmission. If loose to much fluid or air bubbles trapped, hancur, because the engine and transmission have to be on live to do this method.
7) not sure whether applicable to mini transmissions, but need some more canggih cars require scan tool to reset. Didn't properly reset, of course cannot work lor...

But if you changed and still work, it will still continue to work. If got problem, will arise very soon after fluid change, you can rest assured.

When was your last change?

If really got problem, some the very 1st day already can feel something off already.

I don't know what those AB fellors procure for the engine oil, the only thing i know was that BMW HQ decided to preferred engine oil from castrol to shell some years back then and was renewed again last year. So, i hazard guess likely their own house brand oil also from shell.

https://www.shell.com/business-customers/lu...l-supplier.html

Can you describe your last experience regarding "engine running hot"? This statement is quite vague.