What does the server message "Skipping player strafe phase because no player was found" mean?

I got the message "Skipping player strafe phase because no player was found" repeatedly, when a player on my server destroyed the ender dragon. I've never seen it before. Does this imply that he could be using cheats?

Or what is the specific meaning of this message?

We play on a vanilla server.

EDIT: I'm the only OP.

Solution 1:

First, let's try to understand what is being skipped. As the message says, is strafe phase. What is that?

The official minecraft wiki says:

Strafing - the dragon will fly towards the target player. When it is within 64 blocks, it will fire Ender charges and resume circling. If a players destroys an End Crystal, the dragon will immediately switch to this state to fire an Ender Charge at them.

While the question lacks a detailed log, with the information provided I can think of the following outcomes:

• The player destroyed the End Crystals when the Ender Dragon was at 64+ blocks of distance. The wiki mentions that the strafe happens when its within 64 blocks
• The player destroyed the End Crystals AFTER the Ender Dragon was killed, so the dragon position is empty (because its dead) so its not within 64 blocks either
• The player cheated somehow and made it so the Ender Dragon could not detect him as a player, which would also cause a "fail to strafe" message

This is the only things I can consider that caused the message.