Hello. Please consider checking whether you can reproduce the problem - with the .deb package distributed by upstream - in a clean Debian install, if you can start a live system or a chroot. I can see no better way to start investigating this issue.
However... Popcon reports 144 users of the .deb distributed by Debian. There are probably more of them either not running popcon or installing the almost identical .deb from Ubuntu. No one else has reported the same issue for 18 months. Some really run it daily, since unrelated issues have been reported meanwhile. So I intend to reduce the severity to important and allow the package to migrate to testing. important: a bug which has a major effect on the usability of a package, without rendering it completely unusable to everyone.