I have had this problem for as long as I can remember. I thought it might be a plugin, but something odd happened at 1.6.2! I got an unofficial version of bukkit. A one a personal friend had made, and the anvils worked, but as soon as I got the official version of Spigot they broke again I don't receive any errors, but this is what happens. Whenever someone tries to rename a sword or repair one...the new item will show up in the right(Complete)slot. When you click it...it will disappear and take your XP, but you won't get the item. The old item will still be there, but it won't be renamed or repaired. The XP will be gone until you re-log...then it will come back. Now, I am not getting any errors, and this has done this for a LONG time. I am just wondering if anyone knows how to fix it. I am also providing a Plugin list, I know it is a lot, but I actually use them: So, That is about all the information I can provide. Please help me out if possible!