I just noticed that my active and hot are 3 days old, it looks like this server is being hit with this bug where the hot calculator dies. Currently, there are fixes in the works and it may be worth cherry picking them or restarting the server during a down time until the fixes make it into the next release.
I have set a cronjob on my instance to restart Lemmy via docker_compose every 4 hours. It cause a small 30s downtime every 4 hours, but should be preferable to having the timelines stale.