With my flugbuch2 and flightpred projects I had a problem for a while in the debian packages. Namely the installation froze after restarting apache2, while the installation seemed to have succeeded as the websites were accessible. When I reloaded apache instead of restarting, the installation ran through but the websites could not be found.
After endless googling, I found that the debian gallery packages used to suffer the same problem and that it was fixed. So I examined the source. What triggered the problem is an apache installation that’s not properly configured. Namely, if your apache complains that it cannot resolve the fully qualified hostname upon startup, then restarting apache inside my old postinst script would fail the postinst script. It has something to do with debconf waiting on some open file descriptors.
To make it short: move the db_stop to just before the apache restart and that solves the problem.