Comment 12 for bug 1616116

I tested this by deploying landscape-server from ppa:landscape/18.03, connecting clients from {trusty,xenial,bionic,cosmic} against it, restoring a database dump to trigger the issue.
The landscape-clients were then upgraded to *-proposed. As per the test case, the resync loop stopped after.

tail -f /var/log/landscape/package-reporter.log
2019-02-05 19:01:07,139 WARNING [MainThread] Removing cached hash=>id database /var/lib/landscape/client/package/hash-id/2b0e1068-20d4-11e9-8e28-00163e8887ff_bionic_amd64
2019-02-05 19:01:27,315 INFO [MainThread] Queuing message with changes in known packages: 216 installed, 26775 available, 48 available upgrades, 0 locked, 0 autoremovable, 0 not installed, 0 not available, 0 not available upgrades, 0 not locked, 0 not autoremovable.
2019-02-05 19:02:07,812 INFO [MainThread] Downloaded hash=>id database from https://lscape.lxd/hash-id-databases/2b0e1068-20d4-11e9-8e28-00163e8887ff_bionic_amd64

and the server output: https://screenshots.firefox.com/kU7atd0RI411o7r4/lscape.lxd