Game Mechanics: Fear instantly breaks

[finalgrunt]

I've noticed this. Sometimes when I cast fear on a mob, it instantly breaks. But if I recast fear right after, it will instantly break over and over.

For example, if I use the Staff of Dreaded Gaze, and notice an instant break, recasting (spell this time) Invoke Fear will always result in a new instant break. And from there, if I recast the spell on cooldown, instantly breaks.

Here is an example of a log, this time with Staff of Dreaded Gaze only:

[Fri Dec 09 19:01:17 2011] You feel your life force growing.
[Fri Dec 09 19:01:17 2011] A goblin warrior staggers.
[Fri Dec 09 19:01:18 2011] You begin casting Invoke Fear.
[Fri Dec 09 19:01:18 2011] You can't use that command right now...
[Fri Dec 09 19:01:21 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:21 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:21 2011] A goblin warrior tries to kick YOU, but misses!
[Fri Dec 09 19:01:21 2011] a goblin warrior has taken 80 damage from your Bond of Death.
[Fri Dec 09 19:01:24 2011] A goblin warrior hits YOU for 2 points of damage.
[Fri Dec 09 19:01:24 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:25 2011] You regain your concentration and continue your casting.
[Fri Dec 09 19:01:25 2011] Your Invoke Fear spell has worn off.
[Fri Dec 09 19:01:25 2011] A goblin warrior looks very afraid.
[Fri Dec 09 19:01:27 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:27 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:27 2011] You begin casting Invoke Fear.
[Fri Dec 09 19:01:27 2011] a goblin warrior has taken 80 damage from your Bond of Death.
[Fri Dec 09 19:01:29 2011] A goblin warrior tries to kick YOU, but misses!
[Fri Dec 09 19:01:30 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:33 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:33 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:33 2011] a goblin warrior has taken 80 damage from your Bond of Death.
[Fri Dec 09 19:01:34 2011] Your Invoke Fear spell has worn off.
[Fri Dec 09 19:01:34 2011] A goblin warrior looks very afraid.
[Fri Dec 09 19:01:36 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:36 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:37 2011] You begin casting Invoke Fear.
[Fri Dec 09 19:01:37 2011] A goblin warrior tries to kick YOU, but misses!
[Fri Dec 09 19:01:39 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:39 2011] a goblin warrior has taken 80 damage from your Bond of Death.
[Fri Dec 09 19:01:42 2011] A goblin warrior hits YOU for 4 points of damage.
[Fri Dec 09 19:01:44 2011] You regain your concentration and continue your casting.
[Fri Dec 09 19:01:44 2011] Your Invoke Fear spell has worn off.
[Fri Dec 09 19:01:44 2011] A goblin warrior looks very afraid.
[Fri Dec 09 19:01:44 2011] You begin casting Invoke Fear.
[Fri Dec 09 19:01:44 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:44 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:46 2011] a goblin warrior has taken 80 damage from your Bond of Death.
[Fri Dec 09 19:01:46 2011] A goblin warrior tries to kick YOU, but misses!
[Fri Dec 09 19:01:47 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:47 2011] A goblin warrior hits YOU for 26 points of damage.
[Fri Dec 09 19:01:50 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:50 2011] You can't use that command right now...
[Fri Dec 09 19:01:51 2011] You can't use that command right now...
[Fri Dec 09 19:01:51 2011] You regain your concentration and continue your casting.
[Fri Dec 09 19:01:51 2011] Your Invoke Fear spell has worn off.
[Fri Dec 09 19:01:51 2011] A goblin warrior looks very afraid.
[Fri Dec 09 19:01:51 2011] You can't use that command right now...
[Fri Dec 09 19:01:51 2011] You begin casting Invoke Fear.
[Fri Dec 09 19:01:52 2011] a goblin warrior has taken 80 damage from your Bond of Death.
[Fri Dec 09 19:01:53 2011] A goblin warrior hits YOU for 2 points of damage.
[Fri Dec 09 19:01:54 2011] A goblin warrior tries to kick YOU, but misses!
[Fri Dec 09 19:01:56 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:56 2011] A goblin warrior hits YOU for 2 points of damage.
[Fri Dec 09 19:01:57 2011] You can't use that command right now...
[Fri Dec 09 19:01:57 2011] You can't use that command right now...
[Fri Dec 09 19:01:58 2011] a goblin warrior has taken 80 damage from your Bond of Death.
[Fri Dec 09 19:01:58 2011] You can't use that command right now...
[Fri Dec 09 19:01:58 2011] You can't use that command right now...
[Fri Dec 09 19:01:58 2011] You regain your concentration and continue your casting.
[Fri Dec 09 19:01:58 2011] Your Invoke Fear spell has worn off.
[Fri Dec 09 19:01:58 2011] A goblin warrior looks very afraid.
[Fri Dec 09 19:01:59 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:01:59 2011] A goblin warrior hits YOU for 2 points of damage.
[Fri Dec 09 19:02:02 2011] You begin casting Invoke Fear.
[Fri Dec 09 19:02:02 2011] A goblin warrior kicks YOU for 2 points of damage.
[Fri Dec 09 19:02:02 2011] A goblin warrior hits YOU for 2 points of damage.
[Fri Dec 09 19:02:02 2011] You feel your strength return.
[Fri Dec 09 19:02:04 2011] a goblin warrior has taken 80 damage from your Bond of Death.
[Fri Dec 09 19:02:05 2011] A goblin warrior tries to hit YOU, but misses!
[Fri Dec 09 19:02:08 2011] A goblin warrior hits YOU for 2 points of damage.
[Fri Dec 09 19:02:09 2011] You regain your concentration and continue your casting.
[Fri Dec 09 19:02:09 2011] Your Invoke Fear spell has worn off.
[Fri Dec 09 19:02:09 2011] A goblin warrior looks very afraid.
[Fri Dec 09 19:02:10 2011] a goblin warrior was hit by non-melee for 80 points of damage.
[Fri Dec 09 19:02:10 2011] A goblin warrior staggers.
[Fri Dec 09 19:02:10 2011] You have slain a goblin warrior!
[Fri Dec 09 19:02:10 2011] Your faction standing with FirionaVie got better.
[Fri Dec 09 19:02:10 2011] Your faction standing with GoblinsofCleavingTooth could not possibly get any worse.
[Fri Dec 09 19:02:10 2011] Your faction standing with GoblinsofMountainDeath could not possibly get any worse.
[Fri Dec 09 19:02:10 2011] Your faction standing with LegionofCabilis got better.

[Hakurou]

I usually get those kinds of fear breaks if the mob is 'floating' in the air, it can easily be reproduced in the burning woods at the giant fort.

Example: Pull a giant from the fort, run down the ramp and to the side of it so the giant will not walk down the ramp but through the wall (of course without levi or while hugging the floor), he will appear to be on the ground but the server probably still locates the mob higher in the air than the client displays him, fear will instantly break as long as he hasn't walked about the same distance away from the fort as the ramp is long (the point when the mob finally reaches the ground).

Did you per chance use DMF and levitate quite a bit above the ground when trying to fear that goblin, maybe even pull the goblin from a bit away so he 'walked' up into the air? I think the problem here is that the client displays the mob at a different height level than he really is and the server hinders some spells like fear from sticking in an effort to prevent exploits (perhaps mobs in the air can't find a 'fear path' and that breaks fear instantly)? This can also lead to problems when trying to loot corpses. Pull something while levitating way up high and let it die next to you. Visually the corpse will fall to the ground but the corpse location server side is way up in the air and not lootable.

[finalgrunt]

It was a goblin walking on the ground. Happens a looot with bloodgills too.

[DoucLangur]

My first suspicion was a different aspect: Could it be that in those circumstances, the Fear spell did never actually break, but was instead overwritten by your next cast and this erroneously causes the worn off message (as you get it when someone else overwrites your root/snare)? And that a timing bug on serverside causes the goblin to not "notice" it is feared, and behave like an unfeared mob?

The other explanation given sounds more likely, but I thought I would share my thought anyways.

[finalgrunt]

It is not overwritten, as it happens even on the very first cast of fear. And the mob is never feared for subsequent casts. Always breaks instantly.