Server Crashes Intermittently On User Login

Occasionally (every 4-8 attempts), the server will crash when a user attempts to connect. The server hangs after the initial Authenticator check and user joining the game message, at which point a minute later it is killed by the watchdog for no ticks in 60 seconds.

This began occurring on September 13 (well after the update to 1.8 full release after running snapshots since the server's creation). I have 20 crash logs related to this issue.

I have attempted moving the playerdata files so that new ones are forced to be created as a way to resolve the issue, but it continued to occur.

Attached is the most recent crash log as well as a screenshot of the server console at the relevant time.