It seems to be completely random, but I'm constantly spammed with messages in my server console saying things like this:
"Using : vl@139c4bea
Using : vl@dc191
Using : vl@384a2329
Not using : vl@6fb1f837
Using : vl@23560a92
Using : vl@29123da4
Using : vl@283d335a
Using : vl@139c4bea
Using : vl@dc191
Using : vl@384a2329
Not using : vl@7f8f2b5f
Not using : vl@503c97e5
Not using : vl@20bdb60b
Not using : vl@124cd997
Not using : vl@149fcd52
Not using : vl@2028e39b
Not using : vl@6fb1f837
Using : vl@23560a92
Using : vl@29123da4
Using : vl@283d335a
Using : vl@139c4bea
Using : vl@dc191
Using : vl@384a2329"
That text was a direct copy and paste.
The constant stream of messages rarely stop. And when it does, it stops for a few seconds or a few minutes, and then starts right back up again. It does this regardless of the situation. Players or no players. And no, I do not have debug mode enabled.
This makes it very hard to type commands and read the chat.