RT-AC56U System Log stuck? What's this mean?

[Fletch84]

Haven't needed to log into the router in a few weeks.
Saw the new firmware. I'm on 339. Decided to update.
Powered off router. Disconnected WAN cable. Powered up router.
Logged in. Went to look at System Log.

The system log has a lot of dropped packet entries. Typical here.
But the last dropped WAN packet was December 22nd!

Should old logs still be there after a power cycle?
Does the log stop logging when it's full?
Could the logging have gotten stuck and just stopped?

Verified - The firewall is set to "Log Dropped Packets."
I don't mind too much if this is a known logging bug.
What does concern me, the firewall.

Could the firewall and DoS Protection have stopped working on December 22?

 

[Fletch84]

Any guesses why dropped packets stopped being logged?

Has anyone had problems with the logging on rt-ac56u / rt-ac68u,
or do most people just not log dropped packets?