**Minecraft Version:1.11.2
**Server Version:1.11.2
**Inventory Tweaks Version:1.62-dev75

Client will disconnect from server when sorting is done quickly it seems. Can be avoided by waiting in between sorts.

---Begin Client Log---
[18:41:47] [Client thread/INFO]: Handling crafting slots.
[18:41:47] [Client thread/INFO]: Merging stacks.
[18:41:47] [Client thread/INFO]: Applying rules.
[18:41:47] [Client thread/INFO]: Locking stacks.
[18:41:47] [Client thread/INFO]: Default sorting.
[18:41:47] [Client thread/INFO]: Sorting done in 9030137ns
[18:41:47] [Client thread/INFO]: InvTweaks: successfully transformed setFocused/func_146195_b
[chat]
[18:41:50] [Client thread/INFO]: Baking listener list for OutboundChatFilter with 1 listeners
[chat]
[18:42:23] [Client thread/INFO]: Baking listener list for PlayerClickListener with 0 listeners
[chat]
[18:44:56] [Client thread/INFO]: Handling crafting slots.
[18:44:56] [Client thread/INFO]: Merging stacks.
[18:44:56] [Client thread/INFO]: Applying rules.
[18:44:56] [Client thread/INFO]: Locking stacks.
[18:44:56] [Client thread/INFO]: Default sorting.
[18:44:56] [Client thread/INFO]: Sorting done in 2934953ns
[18:44:57] [Client thread/INFO]: Handling crafting slots.
[18:44:57] [Client thread/INFO]: Merging stacks.
[18:44:57] [Client thread/INFO]: Applying rules.
[18:44:57] [Client thread/INFO]: Locking stacks.
[18:44:57] [Client thread/INFO]: Default sorting.
[18:44:57] [Client thread/INFO]: Sorting done in 1620021ns
[chat]
[18:47:09] [Client thread/INFO]: Default sorting.
[18:47:09] [Client thread/INFO]: Sorting done in 5716307ns
[18:47:10] [Client thread/INFO]: Applying holder lookups
[18:47:10] [Client thread/INFO]: Holder lookups applied
This is where the client disconnected, then I reconnected
[18:47:13] [Client thread/INFO]: Connecting to mc.lundus.info, 25565
[18:47:13] [Netty Client IO #1/INFO]: Aborting client handshake "VANILLA"
[18:47:13] [Netty Client IO #1/INFO]: [Netty Client IO #1] Client side vanilla connection established
[18:47:14] [Client thread/INFO]: [CHAT] Welcome, [Admin]~Joshua!
[18:47:14] [Client thread/INFO]: [CHAT] Type /help for a list of commands.
[18:47:14] [Client thread/INFO]: [CHAT] Type /list to see who else is online.
[18:47:14] [Client thread/INFO]: [CHAT] Players online: 3 - World time: 10:55 PM
---End Client Log---

---Begin Server Log---
[18:47:10] [Server thread/INFO]: joshuaw491 lost connection: You are sending too many packets!
---End Server Log---

Hope this info helps.

Yes, the sorting process is fairly heavy, especially in vanilla (/bukkit/spigot/etc.) connection mode.

There's not much that can be done about it, go yell at the plugin or whatever is adding that message because I can't find it anywhere in the vanilla/forge code.