Originally put this comment in the Server Update 6-24 Forum since that's when I first noticed the XTarget problem.  It really got zero response there, so copied it to this thread to keep the XTarget listings condensed. So far the problem remains just as bad as it ever was

"After the server restart on 6-24, I began having problems with my Extended Target Window. During fights, slots in the window were not being cleared out after a NPC was killed. Even though the slot showed blank. It was not really cleared. If you queried the slot with ${Me.XTarget[xx].ID} where xx is the slot number, the slot would return the ID number of the fallen npc that failed to clear.  This happens on 0-5 slots during a fight in random slots, but mainly in slots 1 to 5.  On the next pull the slots that held an ID value would no longer populate, which looked like blank slots in the window. Any uncleared slot would remain unfillable until logging or manually clearing the slot.  Didn't try zoning though ... which may have cleared all slots.

[Edit] Additional Comments:
Additional Data on the problem. On 6-29 in an instance of T10, while working Orcs I continued to have the problem stated above.  I succored my team into the camp and where several camp npcs entered the ETW (ext target window).  To attempt to clear the issue, I logged my team off and back on. Same NPCs came back into the ETW. I then took my team to Nexus and returned to see if that would clear it.  Did not. Finally cleared it by creating a new instance and entering it. Characteristics of the ETW remain the same as the part above, with NPC entries from NPCs far from fight area, blank entries in the window that contain NPC IDs."

Hope this helps, but anyone actively playing the T10 zone with just a few toons in the raid will experience this problem fairly fast ... not hard to demonstrate it.  I've seen all the issues discussed above.

Pet Pulls haywire.

In the last week or so, a problem with the pet pulls has arose.  Recently, the pet is "lost to the imaterium" (sp?) even on short pulls.  However, recently I've only used pulls thru walls, so that may be related. This does not always happen, but does occur roughly 90% of the time, whereas prior to the last few weeks NEVER happened due to the shortness of the pull distance.  Wonder if the recent work on bringing npcs to the surface is related?  In addition, I believe I've noticed that even on successful pulls where the pet is not destroyed, the npc takes longer to get back to the puller (navigating thru the wall maybe?) ... but that may be only my imagination.

I posted a beginning description of the Extended Target Window Problem in the "6/24/2017" Forum subject.  Sorry ... don't know how to start a new subject and Akka's 6/24/2017 subject was the first occurrence of this problem that I noticed. If someone makes a new Forum subject I will move it from that area.

Sorry ... originally put this comment in the 6-20 forum by mistake, so here it is again:

After the server restart, I began having problems with my Extended Target Window. During fights, slots in the window were not being cleared out after a NPC was killed. Even though the slot showed blank. It was not really cleared. If you queried the slot with ${Me.XTarget[xx].ID} where xx is the slot number, the slot would return the ID number of the fallen npc that failed to clear.  This happens on 0-5 slots during a fight in random slots, but mainly in slots 1 to 5.  On the next pull the slots that held an ID value would no longer populate, which looked like blank slots in the window. Any uncleared slot would remain unfillable until logging or manually clearing the slot.  Didn't try zoning though ... which may have cleared all slots.

[Edit] Additional Comments:
Additional Data on the problem. On 6-29 in an instance of T10, while working Orcs I continued to have the problem stated above.  I succored my team into the camp and where several camp npcs entered the ETW (ext target window).  To attempt to clear the issue, I logged my team off and back on. Same NPCs came back into the ETW. I then took my team to Nexus and returned to see if that would clear it.  Did not. Finally cleared it by creating a new instance and entering it. Characteristics of the ETW remain the same as the part above, with NPC entries from NPCs far from fight area, blank entries in the window that contain NPC IDs. Still gathering data.

For what it's worth, here are my problems and symptoms.
I have limited bandwidth (8 Mbps) and typically run about 15 toons.  After the server mod, I can hardly log any of them in and when I am successful on the logon, they usually desync within a few minutes.  After a particular toon desync's, it is very very hard to get that toon relogged in, wheras other toons can be successful. Typically after the character selection screen ... long waits are incurred, resulting in a timeout.

On successful logins, I desync without any main activity ... no pulling, fighting, etc.  On one occasion after successfully logging in 2 toons, I issued a simple "/raidinvite [othertoonname]" and it took 7-10 seconds for the target toon to get the request. So it seems handshaking is a factor.  Before mods, none of these issues persisted.

I'm very limited on what I can test ... but am certainly willing if additional data would help.  As it remains now, the system is unplayable.