It's a bug. Why should a software bug have an effect on a manufacturer's stock price? It's not like the update caused brake failures or something.
> or something
Maybe do some research into the problem you're confidently asserting was trivial / read the article you're commenting on:
"...others claim to have experienced a powertrain failure at highway speeds."
https://www.reddit.com/r/Jeep/comments/1o47064/jeep_4xe_shut...
There's a reason their slogan is "(you don't understand), It's a jeep thing"
They're a lifestyle product and have been for decades. Most of Stellantis is.