I'm having this same bug.
My custom animated swords are freezing on one frame once I enchant them.
Mine seem to only freeze the animation if it is a sword summoned by the /give command.
/give @p diamond_sword{CustomModelData: 2}
Enchant that sword and the animation freezes.
Duplicate the sword and enchant the duplicate version and the animation continues playing once enchanted!
Upon further testing, when chests are created with the items as enchanted loot, sometimes they animate, other times they don't!
A little video showing what is happening:
https://www.youtube.com/watch?v=Io7iyW2r3mY
I'm getting the netty error on my self-built server running Minecraft 1.7.10
When I connect, even if using the same PC to connect to the local machine I can play for maybe a minute, then I get the timeout error and the server stops responding and I have to force close it as the 'stop' command does nothing. Checking in task manager and the server does max out my CPU usage. I have it set to run only on two cores currently but even if I leave it to run on all four cores it stops around the 75-85% CPU usage!
I also keep getting the [19:16:48] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 2998ms behind, skipping 59 tick(s) message, straight after starting up the server, before anybody has attempted to log on!
I have attached the resource pack I was using, if that helps at all.