There’s an odd bug in ipfw that is now fixed in DragonFly 6.2/6.3. If you are using ipfw and adding networks and hosts in a specific order, the netmask will be set wrong.
There’s also a problem with the overnight bulkfree cleanup in Hammer that’s had various attempts to fix it over time – it’s now really truly fixed. It mattered only if you had an extremely large number of inodes – 100000000 or so,
Matthew Dillon wrote up an explanation for both.