They ship cars with steering wheels that fall off, this is pretty tame in comparison.

At a former SaaS startup my colleague rolled out some updates that affected an apache module's connection pooling persistence defaults.

Everything had worked fine in his testing, but once in production there was enough concurrency to make this change in caching behavior matter. One customer's web login would spuriously see another customer's content, it all seemed completely random.

A similar change (or rare bug) could easily result in one customer's boolean "yes they're allowed" reach another who should have received "no they're not". There's all sorts of opportunities in the backend to cross such streams, especially things that need to scale and do a lot of caching.

Tesla ships 400k cars per quarter. AFAIK this is the only case reported of this. It sounds like BS.

If the least few months have taught us anything, it's that Elon Musk is not big on testing things before they go to production.

What testing?