Not sure what we can do here. Is the error logged? If you use FPM, you'd even not be able to see the error, because of fastcgi_finish_request. What is displayed in stderr in php -S mode? Is there a profiler page with the exception reported?
Honestly, there are some cases where either Symfony or PHP is shutting down, and we cannot do better...

Maybe we can catch the error, and display an alternative message instead with a link to the profiler?

Let's close. Using kernel.terminate is very dangerous and should be avoided at all costs. Here, the Messenger component helps a lot as we now have a core built-in way of doing things out of band.

@fabpot : Out of curiosity, why do you think it is very dangerous and what would you think about #28646? Should we avoid doing it? That's cheap, but can be valuable on some projects.

For #28646, I'm the one who suggested it, so I'm fine with it as a poor man solution :)

@ogizanagi kernel.terminate is meant to run the logic after the Response was sent. This means that we cannot provide any feedback about what is happening at that time (that's too late for sending feedback about failure)