https://bugs.kde.org/show_bug.cgi?id=463576 and https://bugs.kde.org/show_bug.cgi?id=462706 appears to be the obvious upstream kde bug.
which implicates PackageKit: https://github.com/PackageKit/PackageKit-Qt/issues/42 which has https://github.com/PackageKit/PackageKit-Qt/pull/45 as a potential fix. Also as a hacky workaround, the bug seems to occur when updating the package lists, if you've recently refreshed the package lists (eg via "apt update") then the bug isn't triggered.
