Undocking triggers PLAYER_LEFT_SECTOR, then PLAYER_ENTERED_SECTOR events.
odd?

Have you updated to the latest client version?

Did the player in question change ships?

I noticed this today when I chased a Moth to a station, and they undocked in an Atlas. Didn't notice it on anyone else that undocked while I was stalking them. And yes, my client is up-to date.

Yes, ray, this is not upon entry of a sector, but undocking. It remains even through the patch of 1.8.200

EDIT: yoda, I don't think so.

Ok, confirmed: An undocking player sends out PLAYER_LEFT_SECTOR, then PLAYER_ENTERED_SECTOR events, but also killing someone in a station sector they are homed in also triggers it.

[12/17/11 08:28:40] You are entering Azek D-11
*Cameraman4: Behemoth Heavy Miner - 100% health 3204m away :: I:Admire S:Respect U:Admire L:Admire
[12/17/11 08:29:16] You have violated the local No-Fire zone regulations. Temporary Kill On Sight standing set. Leave the sector immediately, or be destroyed!
[12/17/11 08:29:18] yodaofborg destroyed Cameraman4
Cameraman4: Left the sector. (PLAYER_LEFT_SECTOR)
Cameraman4: Out of range. (PLAYER_ENTERED_SECTOR)