Bukkit Help Needed(Arrows move one block above after hit wall)

Hey there people, I am finding a glitch in my Minecraft Bukkit server.
The MC Version is 1.6 and the Build is 860.
Plugins I use:
-Essentials Suite
(Including group manager)
-ColorMe
-RocketBoots
-MoveCraft
-MultiVerse
-Spyer
-LWC
-GodPowers
-Flatland
-Runecraft
-EpicZones
-Citizens(NPCs)

I think that's all lol


The glitch is that when I shot an arrow after it hits an wall after some time it simply moves up a block???

Bump? (is this allowed?)

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

bumpbump???

 

its supposed to be like this

 

wtf? Why?
Anyway, I tested my server with the same build but removed the plugins, and it was still the same, so I'll try updating my bukkit to the new one released this weeked...

Still didn't work... Any ideas?
Btw does this happen to everyone else? Cause I was still the same after I removed the plugins(?)

EDIT by Moderator: merged posts, please use the edit button instead of double posting.