I was running xdebug and stopped on a breakpoint. so far so good, but after 40-45 seconds the site redirected to a page that displayed an internal server error.
I have the extension running and by default the max_execution_time is 1200. I also checked php.ini, but no value is below 40 seconds.
Has this to do with a timeout or is this something else?
It is solved. It was an Apache problem. Apache times out by default after 40 seconds on a breakpoint. I added FcgidIOTimeout 600 to site.conf.hbs withing the <ifModule...> section to increase this to 10 minutes.